diff --git a/.jshintrc b/.jshintrc
index 96e43ec6..4cf0db5e 100644
--- a/.jshintrc
+++ b/.jshintrc
@@ -1,7 +1,7 @@
 {
     "camelcase": true,
     "curly": true,
-    "eqnull": true,
+    "eqeqeq": true,
     "forin": true,
     "immed": true,
     "indent": 4,
@@ -11,8 +11,9 @@
     "noempty": true,
     "nonbsp": true,
     "quotmark": "double",
-    "unused": true,
+    "strict": true,
     "undef": true,
+    "unused": true,
     "globals": {
         "CSSLint": true,
         "YUITest": true
diff --git a/Gruntfile.js b/Gruntfile.js
index 3ecf8884..d8c264ba 100644
--- a/Gruntfile.js
+++ b/Gruntfile.js
@@ -1,5 +1,7 @@
 /* jshint camelcase:false, evil:true, node:true */
 
+"use strict";
+
 module.exports = function(grunt) {
 
     // Project configuration.
diff --git a/demos/CSSLintDemo.htm b/demos/CSSLintDemo.htm
index 3e60ea0b..15a771b1 100644
--- a/demos/CSSLintDemo.htm
+++ b/demos/CSSLintDemo.htm
@@ -78,6 +78,7 @@ <h1>CSSLint Demo</h1>
     <div id="output"></div>
     <script>
         (function() {
+            "use strict";
 
             document.body.onclick = function(event) {
                 event = event || window.event;
@@ -85,7 +86,7 @@ <h1>CSSLint Demo</h1>
                     results, messages, i, len;
 
 
-                if (target.id == "lint-btn") {
+                if (target.id === "lint-btn") {
                     document.getElementById("output").innerHTML = "";
                     results = CSSLint.verify(document.getElementById("input").value);
                     messages = results.messages;
diff --git a/src/cli/common.js b/src/cli/common.js
index fd6867bb..07927393 100644
--- a/src/cli/common.js
+++ b/src/cli/common.js
@@ -6,6 +6,7 @@
 /* exported cli */
 
 function cli(api){
+    "use strict";
 
     var globalOptions = {
         "help"        : { "format" : "",                       "description" : "Displays this information."},
diff --git a/src/cli/node.js b/src/cli/node.js
index caa1faf8..662f531a 100644
--- a/src/cli/node.js
+++ b/src/cli/node.js
@@ -14,14 +14,17 @@ cli({
     args: process.argv.slice(2),
 
     print: function(message){
+        "use strict";
         fs.writeSync(1, message + "\n");
     },
 
     quit: function(code){
+        "use strict";
         process.exit(code || 0);
     },
 
     isDirectory: function(name){
+        "use strict";
         try {
             return fs.statSync(name).isDirectory();
         } catch (ex) {
@@ -30,6 +33,7 @@ cli({
     },
 
     getFiles: function(dir){
+        "use strict";
         var files = [];
 
         try {
@@ -44,7 +48,7 @@ cli({
                 var path = stack.concat([file]).join("/"),
                     stat = fs.statSync(path);
 
-                if (file[0] == ".") {
+                if (file[0] === ".") {
                     return;
                 } else if (stat.isFile() && /\.css$/.test(file)){
                     files.push(path);
@@ -61,14 +65,17 @@ cli({
     },
 
     getWorkingDirectory: function() {
+        "use strict";
         return process.cwd();
     },
 
     getFullPath: function(filename){
+        "use strict";
         return path.resolve(process.cwd(), filename);
     },
 
     readFile: function(filename){
+        "use strict";
         try {
             return fs.readFileSync(filename, "utf-8");
         } catch (ex) {
diff --git a/src/cli/rhino.js b/src/cli/rhino.js
index c1ef2009..feff21a5 100644
--- a/src/cli/rhino.js
+++ b/src/cli/rhino.js
@@ -8,16 +8,19 @@
 importPackage(java.io);
 
 cli({
+
     args: Array.prototype.concat.call(arguments),
     print: print,
     quit: quit,
 
     isDirectory: function(name){
+        "use strict";
         var dir = new File(name);
         return dir.isDirectory();
     },
 
     getFiles: function(dir){
+        "use strict";
         var files = [];
 
         function traverse(dir) {
@@ -37,14 +40,17 @@ cli({
     },
 
     getWorkingDirectory: function() {
+        "use strict";
         return (new File(".")).getCanonicalPath();
     },
 
     getFullPath: function(filename){
+        "use strict";
         return (new File(filename)).getCanonicalPath();
     },
 
     readFile: function(filename) {
+        "use strict";
         try {
             return readFile(filename);
         } catch (ex) {
diff --git a/src/cli/wsh.js b/src/cli/wsh.js
index d961c0e9..7f587071 100644
--- a/src/cli/wsh.js
+++ b/src/cli/wsh.js
@@ -8,6 +8,8 @@
 /* global cli */
 
 var wshapi = (function(){
+    "use strict";
+
     var fso = new ActiveXObject("Scripting.FileSystemObject");
     var shell = WScript.CreateObject("WScript.Shell");
     var finalArgs = [], i, args = WScript.Arguments;
@@ -22,7 +24,7 @@ var wshapi = (function(){
 
     if (typeof Array.prototype.filter !== "function") {
         Array.prototype.filter = function(fn /*, thisp*/) {
-            if (typeof fn != "function") {
+            if (typeof fn !== "function") {
                 throw new Error("not a function");
             }
             var res = [], val, thisp = finalArgs[1];
@@ -41,7 +43,6 @@ var wshapi = (function(){
 
     if (!Array.prototype.indexOf) {
         Array.prototype.indexOf = function (searchElement /*, fromIndex */ ) {
-            "use strict";
             if (this === void 0 || this === null) {
                 throw new Error("unknown instance");
             }
diff --git a/src/core/CSSLint.js b/src/core/CSSLint.js
index 321a93f6..61e41706 100644
--- a/src/core/CSSLint.js
+++ b/src/core/CSSLint.js
@@ -9,6 +9,7 @@
 /* exported CSSLint */
 
 var CSSLint = (function(){
+    "use strict";
 
     var rules           = [],
         formatters      = [],
diff --git a/src/core/Reporter.js b/src/core/Reporter.js
index 71200563..61660de2 100644
--- a/src/core/Reporter.js
+++ b/src/core/Reporter.js
@@ -8,6 +8,7 @@
  *      they are errors or warnings.
  */
 function Reporter(lines, ruleset){
+    "use strict";
 
     /**
      * List of messages being reported.
@@ -54,6 +55,7 @@ Reporter.prototype = {
      * @method error
      */
     error: function(message, line, col, rule){
+        "use strict";
         this.messages.push({
             type    : "error",
             line    : line,
@@ -74,6 +76,7 @@ Reporter.prototype = {
      * @deprecated Use report instead.
      */
     warn: function(message, line, col, rule){
+        "use strict";
         this.report(message, line, col, rule);
     },
 
@@ -86,8 +89,9 @@ Reporter.prototype = {
      * @method report
      */
     report: function(message, line, col, rule){
+        "use strict";
         this.messages.push({
-            type    : this.ruleset[rule.id] == 2 ? "error" : "warning",
+            type    : this.ruleset[rule.id] === 2 ? "error" : "warning",
             line    : line,
             col     : col,
             message : message,
@@ -105,6 +109,7 @@ Reporter.prototype = {
      * @method info
      */
     info: function(message, line, col, rule){
+        "use strict";
         this.messages.push({
             type    : "info",
             line    : line,
@@ -122,6 +127,7 @@ Reporter.prototype = {
      * @method rollupError
      */
     rollupError: function(message, rule){
+        "use strict";
         this.messages.push({
             type    : "error",
             rollup  : true,
@@ -137,6 +143,7 @@ Reporter.prototype = {
      * @method rollupWarn
      */
     rollupWarn: function(message, rule){
+        "use strict";
         this.messages.push({
             type    : "warning",
             rollup  : true,
@@ -152,6 +159,7 @@ Reporter.prototype = {
      * @method stat
      */
     stat: function(name, value){
+        "use strict";
         this.stats[name] = value;
     }
 };
diff --git a/src/core/Util.js b/src/core/Util.js
index 90ef1ebf..f804ab15 100644
--- a/src/core/Util.js
+++ b/src/core/Util.js
@@ -11,6 +11,7 @@ CSSLint.Util = {
      * @return {Object} The receiver
      */
     mix: function(receiver, supplier){
+        "use strict";
         var prop;
 
         for (prop in supplier){
@@ -29,6 +30,7 @@ CSSLint.Util = {
      * @return {int} The index of the value if found, -1 if not.
      */
     indexOf: function(values, value){
+        "use strict";
         if (values.indexOf){
             return values.indexOf(value);
         } else {
@@ -48,6 +50,7 @@ CSSLint.Util = {
      * @return {void}
      */
     forEach: function(values, func) {
+        "use strict";
         if (values.forEach){
             return values.forEach(func);
         } else {
diff --git a/src/formatters/checkstyle-xml.js b/src/formatters/checkstyle-xml.js
index e1e51e77..d95126cd 100644
--- a/src/formatters/checkstyle-xml.js
+++ b/src/formatters/checkstyle-xml.js
@@ -1,4 +1,5 @@
 (function() {
+    "use strict";
 
     /**
      * Replace special characters before write to output.
diff --git a/src/formatters/compact.js b/src/formatters/compact.js
index 0629cbfe..ef86148d 100644
--- a/src/formatters/compact.js
+++ b/src/formatters/compact.js
@@ -8,6 +8,7 @@ CSSLint.addFormatter({
      * @return {String} to prepend before all results
      */
     startFormat: function() {
+        "use strict";
         return "";
     },
 
@@ -16,6 +17,7 @@ CSSLint.addFormatter({
      * @return {String} to append after all results
      */
     endFormat: function() {
+        "use strict";
         return "";
     },
 
@@ -27,6 +29,7 @@ CSSLint.addFormatter({
      * @return {String} output for results
      */
     formatResults: function(results, filename, options) {
+        "use strict";
         var messages = results.messages,
             output = "";
         options = options || {};
@@ -41,7 +44,7 @@ CSSLint.addFormatter({
         };
 
         if (messages.length === 0) {
-            return options.quiet ? "" : filename + ": Lint Free!";
+              return options.quiet ? "" : filename + ": Lint Free!";
         }
 
         CSSLint.Util.forEach(messages, function(message) {
diff --git a/src/formatters/csslint-xml.js b/src/formatters/csslint-xml.js
index 88b48a0b..4720bc2b 100644
--- a/src/formatters/csslint-xml.js
+++ b/src/formatters/csslint-xml.js
@@ -8,6 +8,7 @@ CSSLint.addFormatter({
      * @return {String} to prepend before all results
      */
     startFormat: function(){
+        "use strict";
         return "<?xml version=\"1.0\" encoding=\"utf-8\"?><csslint>";
     },
 
@@ -16,6 +17,7 @@ CSSLint.addFormatter({
      * @return {String} to append after all results
      */
     endFormat: function(){
+        "use strict";
         return "</csslint>";
     },
 
@@ -27,6 +29,7 @@ CSSLint.addFormatter({
      * @return {String} output for results
      */
     formatResults: function(results, filename/*, options*/) {
+        "use strict";
         var messages = results.messages,
             output = [];
 
diff --git a/src/formatters/junit-xml.js b/src/formatters/junit-xml.js
index 0415d8c0..e0187aae 100644
--- a/src/formatters/junit-xml.js
+++ b/src/formatters/junit-xml.js
@@ -8,6 +8,7 @@ CSSLint.addFormatter({
      * @return {String} to prepend before all results
      */
     startFormat: function(){
+        "use strict";
         return "<?xml version=\"1.0\" encoding=\"utf-8\"?><testsuites>";
     },
 
@@ -16,6 +17,7 @@ CSSLint.addFormatter({
      * @return {String} to append after all results
      */
     endFormat: function() {
+        "use strict";
         return "</testsuites>";
     },
 
@@ -27,6 +29,7 @@ CSSLint.addFormatter({
      * @return {String} output for results
      */
     formatResults: function(results, filename/*, options*/) {
+        "use strict";
 
         var messages = results.messages,
             output = [],
diff --git a/src/formatters/lint-xml.js b/src/formatters/lint-xml.js
index 9e1eac05..653bb20a 100644
--- a/src/formatters/lint-xml.js
+++ b/src/formatters/lint-xml.js
@@ -8,6 +8,7 @@ CSSLint.addFormatter({
      * @return {String} to prepend before all results
      */
     startFormat: function(){
+        "use strict";
         return "<?xml version=\"1.0\" encoding=\"utf-8\"?><lint>";
     },
 
@@ -16,6 +17,7 @@ CSSLint.addFormatter({
      * @return {String} to append after all results
      */
     endFormat: function(){
+        "use strict";
         return "</lint>";
     },
 
@@ -27,6 +29,7 @@ CSSLint.addFormatter({
      * @return {String} output for results
      */
     formatResults: function(results, filename/*, options*/) {
+        "use strict";
         var messages = results.messages,
             output = [];
 
diff --git a/src/formatters/text.js b/src/formatters/text.js
index d0669f86..9af250d7 100644
--- a/src/formatters/text.js
+++ b/src/formatters/text.js
@@ -8,6 +8,7 @@ CSSLint.addFormatter({
      * @return {String} to prepend before all results
      */
     startFormat: function() {
+        "use strict";
         return "";
     },
 
@@ -16,6 +17,7 @@ CSSLint.addFormatter({
      * @return {String} to append after all results
      */
     endFormat: function() {
+        "use strict";
         return "";
     },
 
@@ -27,6 +29,7 @@ CSSLint.addFormatter({
      * @return {String} output for results
      */
     formatResults: function(results, filename, options) {
+        "use strict";
         var messages = results.messages,
             output = "";
         options = options || {};
@@ -36,7 +39,7 @@ CSSLint.addFormatter({
         }
 
         output = "\n\ncsslint: There ";
-        if (messages.length == 1) {
+        if (messages.length === 1) {
             output += "is 1 problem";
         } else {
             output += "are " + messages.length  +  " problems";
diff --git a/src/rules/adjoining-classes.js b/src/rules/adjoining-classes.js
index f23094c9..5f335034 100644
--- a/src/rules/adjoining-classes.js
+++ b/src/rules/adjoining-classes.js
@@ -12,6 +12,7 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter){
+        "use strict";
         var rule = this;
         parser.addListener("startrule", function(event){
             var selectors = event.selectors,
@@ -25,11 +26,11 @@ CSSLint.addRule({
                 selector = selectors[i];
                 for (j=0; j < selector.parts.length; j++){
                     part = selector.parts[j];
-                    if (part.type == parser.SELECTOR_PART_TYPE){
+                    if (part.type === parser.SELECTOR_PART_TYPE){
                         classCount = 0;
                         for (k=0; k < part.modifiers.length; k++){
                             modifier = part.modifiers[k];
-                            if (modifier.type == "class"){
+                            if (modifier.type === "class"){
                                 classCount++;
                             }
                             if (classCount > 1){
diff --git a/src/rules/box-model.js b/src/rules/box-model.js
index dcd57571..9bd1fef8 100644
--- a/src/rules/box-model.js
+++ b/src/rules/box-model.js
@@ -11,6 +11,7 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter){
+        "use strict";
         var rule = this,
             widthProperties = {
                 border: 1,
@@ -45,7 +46,7 @@ CSSLint.addRule({
                         if (heightProperties.hasOwnProperty(prop) && properties[prop]){
                             value = properties[prop].value;
                             //special case for padding
-                            if (!(prop == "padding" && value.parts.length === 2 && value.parts[0].value === 0)){
+                            if (!(prop === "padding" && value.parts.length === 2 && value.parts[0].value === 0)){
                                 reporter.report("Using height with " + prop + " can sometimes make elements larger than you expect.", properties[prop].line, properties[prop].col, rule);
                             }
                         }
@@ -57,7 +58,7 @@ CSSLint.addRule({
                         if (widthProperties.hasOwnProperty(prop) && properties[prop]){
                             value = properties[prop].value;
 
-                            if (!(prop == "padding" && value.parts.length === 2 && value.parts[1].value === 0)){
+                            if (!(prop === "padding" && value.parts.length === 2 && value.parts[1].value === 0)){
                                 reporter.report("Using width with " + prop + " can sometimes make elements larger than you expect.", properties[prop].line, properties[prop].col, rule);
                             }
                         }
@@ -76,13 +77,13 @@ CSSLint.addRule({
             var name = event.property.text.toLowerCase();
 
             if (heightProperties[name] || widthProperties[name]){
-                if (!/^0\S*$/.test(event.value) && !(name == "border" && event.value == "none")){
+                if (!/^0\S*$/.test(event.value) && !(name === "border" && event.value.toString() === "none")){
                     properties[name] = { line: event.property.line, col: event.property.col, value: event.value };
                 }
             } else {
                 if (/^(width|height)/i.test(name) && /^(length|percentage)/.test(event.value.parts[0].type)){
                     properties[name] = 1;
-                } else if (name == "box-sizing") {
+                } else if (name === "box-sizing") {
                     boxSizing = true;
                 }
             }
diff --git a/src/rules/box-sizing.js b/src/rules/box-sizing.js
index ee7e7a07..d6a34816 100644
--- a/src/rules/box-sizing.js
+++ b/src/rules/box-sizing.js
@@ -13,12 +13,13 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter){
+        "use strict";
         var rule = this;
 
         parser.addListener("property", function(event){
             var name = event.property.text.toLowerCase();
 
-            if (name == "box-sizing"){
+            if (name === "box-sizing"){
                 reporter.report("The box-sizing property isn't supported in IE6 and IE7.", event.line, event.col, rule);
             }
         });
diff --git a/src/rules/bulletproof-font-face.js b/src/rules/bulletproof-font-face.js
index 6958e89b..c5c67d7e 100644
--- a/src/rules/bulletproof-font-face.js
+++ b/src/rules/bulletproof-font-face.js
@@ -13,6 +13,7 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter){
+        "use strict";
         var rule = this,
             fontFaceRule = false,
             firstSrc     = true,
diff --git a/src/rules/compatible-vendor-prefixes.js b/src/rules/compatible-vendor-prefixes.js
index d8408d46..ba86bb56 100644
--- a/src/rules/compatible-vendor-prefixes.js
+++ b/src/rules/compatible-vendor-prefixes.js
@@ -13,6 +13,7 @@ CSSLint.addRule({
 
     //initialization
     init: function (parser, reporter) {
+        "use strict";
         var rule = this,
             compatiblePrefixes,
             properties,
@@ -116,7 +117,7 @@ CSSLint.addRule({
             if (CSSLint.Util.indexOf(applyTo, name.text) > -1) {
 
                 // e.g., -moz-transform is okay to be alone in @-moz-keyframes
-                if (!inKeyFrame || typeof inKeyFrame != "string" ||
+                if (!inKeyFrame || typeof inKeyFrame !== "string" ||
                         name.text.indexOf("-" + inKeyFrame + "-") !== 0) {
                     properties.push(name);
                 }
@@ -173,7 +174,7 @@ CSSLint.addRule({
                         for (i = 0, len = full.length; i < len; i++) {
                             item = full[i];
                             if (CSSLint.Util.indexOf(actual, item) === -1) {
-                                propertiesSpecified = (actual.length === 1) ? actual[0] : (actual.length == 2) ? actual.join(" and ") : actual.join(", ");
+                                propertiesSpecified = (actual.length === 1) ? actual[0] : (actual.length === 2) ? actual.join(" and ") : actual.join(", ");
                                 reporter.report("The property " + item + " is compatible with " + propertiesSpecified + " and should be included as well.", value.actualNodes[0].line, value.actualNodes[0].col, rule);
                             }
                         }
diff --git a/src/rules/display-property-grouping.js b/src/rules/display-property-grouping.js
index 15d48d1e..ab4a2fc6 100644
--- a/src/rules/display-property-grouping.js
+++ b/src/rules/display-property-grouping.js
@@ -16,6 +16,7 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter){
+        "use strict";
         var rule = this;
 
         var propertiesToCheck = {
@@ -39,7 +40,7 @@ CSSLint.addRule({
 
         function reportProperty(name, display, msg){
             if (properties[name]){
-                if (typeof propertiesToCheck[name] != "string" || properties[name].value.toLowerCase() != propertiesToCheck[name]){
+                if (typeof propertiesToCheck[name] !== "string" || properties[name].value.toLowerCase() !== propertiesToCheck[name]){
                     reporter.report(msg || name + " can't be used with display: " + display + ".", properties[name].line, properties[name].col, rule);
                 }
             }
diff --git a/src/rules/duplicate-background-images.js b/src/rules/duplicate-background-images.js
index a9fee588..b476e750 100644
--- a/src/rules/duplicate-background-images.js
+++ b/src/rules/duplicate-background-images.js
@@ -12,6 +12,7 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter){
+        "use strict";
         var rule = this,
             stack = {};
 
@@ -22,7 +23,7 @@ CSSLint.addRule({
 
             if (name.match(/background/i)) {
                 for (i=0, len=value.parts.length; i < len; i++) {
-                    if (value.parts[i].type == "uri") {
+                    if (value.parts[i].type === "uri") {
                         if (typeof stack[value.parts[i].uri] === "undefined") {
                             stack[value.parts[i].uri] = event;
                         }
diff --git a/src/rules/duplicate-properties.js b/src/rules/duplicate-properties.js
index 1333d3f1..239a46f0 100644
--- a/src/rules/duplicate-properties.js
+++ b/src/rules/duplicate-properties.js
@@ -13,6 +13,7 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter){
+        "use strict";
         var rule = this,
             properties,
             lastProperty;
@@ -31,7 +32,7 @@ CSSLint.addRule({
             var property = event.property,
                 name = property.text.toLowerCase();
 
-            if (properties[name] && (lastProperty != name || properties[name] == event.value.text)){
+            if (properties[name] && (lastProperty !== name || properties[name] === event.value.text)){
                 reporter.report("Duplicate property '" + event.property + "' found.", event.line, event.col, rule);
             }
 
diff --git a/src/rules/empty-rules.js b/src/rules/empty-rules.js
index 2048b989..2f9c94c9 100644
--- a/src/rules/empty-rules.js
+++ b/src/rules/empty-rules.js
@@ -12,6 +12,7 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter){
+        "use strict";
         var rule = this,
             count = 0;
 
diff --git a/src/rules/errors.js b/src/rules/errors.js
index b732e5f3..08c1da39 100644
--- a/src/rules/errors.js
+++ b/src/rules/errors.js
@@ -12,6 +12,7 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter){
+        "use strict";
         var rule = this;
 
         parser.addListener("error", function(event){
diff --git a/src/rules/fallback-colors.js b/src/rules/fallback-colors.js
index 79f3b74e..f3498ca3 100644
--- a/src/rules/fallback-colors.js
+++ b/src/rules/fallback-colors.js
@@ -8,6 +8,7 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter){
+        "use strict";
         var rule = this,
             lastProperty,
             propertiesToCheck = {
@@ -48,14 +49,14 @@ CSSLint.addRule({
 
             if(propertiesToCheck[name]){
                 while(i < len){
-                    if (parts[i].type == "color"){
+                    if (parts[i].type === "color"){
                         if ("alpha" in parts[i] || "hue" in parts[i]){
 
                             if (/([^\)]+)\(/.test(parts[i])){
                                 colorType = RegExp.$1.toUpperCase();
                             }
 
-                            if (!lastProperty || (lastProperty.property.text.toLowerCase() != name || lastProperty.colorType != "compat")){
+                            if (!lastProperty || (lastProperty.property.text.toLowerCase() !== name || lastProperty.colorType !== "compat")){
                                 reporter.report("Fallback " + name + " (hex or RGB) should precede " + colorType + " " + name + ".", event.line, event.col, rule);
                             }
                         } else {
diff --git a/src/rules/floats.js b/src/rules/floats.js
index 5dbfb99f..098c9254 100644
--- a/src/rules/floats.js
+++ b/src/rules/floats.js
@@ -13,13 +13,14 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter){
+        "use strict";
         var rule = this;
         var count = 0;
 
         //count how many times "float" is used
         parser.addListener("property", function(event){
-            if (event.property.text.toLowerCase() == "float" &&
-                    event.value.text.toLowerCase() != "none"){
+            if (event.property.text.toLowerCase() === "float" &&
+                    event.value.text.toLowerCase() !== "none"){
                 count++;
             }
         });
diff --git a/src/rules/font-faces.js b/src/rules/font-faces.js
index 10c9e735..b349cd27 100644
--- a/src/rules/font-faces.js
+++ b/src/rules/font-faces.js
@@ -12,6 +12,7 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter){
+        "use strict";
         var rule = this,
             count = 0;
 
diff --git a/src/rules/font-sizes.js b/src/rules/font-sizes.js
index 20f96ceb..85b06cff 100644
--- a/src/rules/font-sizes.js
+++ b/src/rules/font-sizes.js
@@ -12,12 +12,13 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter){
+        "use strict";
         var rule = this,
             count = 0;
 
         //check for use of "font-size"
         parser.addListener("property", function(event){
-            if (event.property == "font-size"){
+            if (event.property.toString() === "font-size"){
                 count++;
             }
         });
diff --git a/src/rules/gradients.js b/src/rules/gradients.js
index 77f27e95..2e0fa22c 100644
--- a/src/rules/gradients.js
+++ b/src/rules/gradients.js
@@ -12,6 +12,7 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter){
+        "use strict";
         var rule = this,
             gradients;
 
diff --git a/src/rules/ids.js b/src/rules/ids.js
index 04c877bc..28890395 100644
--- a/src/rules/ids.js
+++ b/src/rules/ids.js
@@ -12,6 +12,7 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter){
+        "use strict";
         var rule = this;
         parser.addListener("startrule", function(event){
             var selectors = event.selectors,
@@ -27,17 +28,17 @@ CSSLint.addRule({
 
                 for (j=0; j < selector.parts.length; j++){
                     part = selector.parts[j];
-                    if (part.type == parser.SELECTOR_PART_TYPE){
+                    if (part.type === parser.SELECTOR_PART_TYPE){
                         for (k=0; k < part.modifiers.length; k++){
                             modifier = part.modifiers[k];
-                            if (modifier.type == "id"){
+                            if (modifier.type === "id"){
                                 idCount++;
                             }
                         }
                     }
                 }
 
-                if (idCount == 1){
+                if (idCount === 1){
                     reporter.report("Don't use IDs in selectors.", selector.line, selector.col, rule);
                 } else if (idCount > 1){
                     reporter.report(idCount + " IDs in the selector, really?", selector.line, selector.col, rule);
diff --git a/src/rules/import.js b/src/rules/import.js
index 67b51e0a..4f0a5435 100644
--- a/src/rules/import.js
+++ b/src/rules/import.js
@@ -12,6 +12,7 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter){
+        "use strict";
         var rule = this;
 
         parser.addListener("import", function(event){
diff --git a/src/rules/important.js b/src/rules/important.js
index 0c53b664..b7436660 100644
--- a/src/rules/important.js
+++ b/src/rules/important.js
@@ -14,6 +14,7 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter){
+        "use strict";
         var rule = this,
             count = 0;
 
diff --git a/src/rules/known-properties.js b/src/rules/known-properties.js
index 711ff501..b56fa9e2 100644
--- a/src/rules/known-properties.js
+++ b/src/rules/known-properties.js
@@ -13,6 +13,7 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter){
+        "use strict";
         var rule = this;
 
         parser.addListener("property", function(event){
diff --git a/src/rules/order-alphabetical.js b/src/rules/order-alphabetical.js
index 84386ac3..9c8ac18b 100644
--- a/src/rules/order-alphabetical.js
+++ b/src/rules/order-alphabetical.js
@@ -12,6 +12,7 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter){
+        "use strict";
         var rule = this,
             properties;
 
diff --git a/src/rules/outline-none.js b/src/rules/outline-none.js
index 7953a3d5..dc0c9657 100644
--- a/src/rules/outline-none.js
+++ b/src/rules/outline-none.js
@@ -14,6 +14,7 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter){
+        "use strict";
         var rule = this,
             lastRule;
 
@@ -34,9 +35,9 @@ CSSLint.addRule({
         function endRule(){
             if (lastRule){
                 if (lastRule.outline){
-                    if (lastRule.selectors.toString().toLowerCase().indexOf(":focus") == -1){
+                    if (lastRule.selectors.toString().toLowerCase().indexOf(":focus") === -1){
                         reporter.report("Outlines should only be modified using :focus.", lastRule.line, lastRule.col, rule);
-                    } else if (lastRule.propCount == 1) {
+                    } else if (lastRule.propCount === 1) {
                         reporter.report("Outlines shouldn't be hidden unless other visual changes are made.", lastRule.line, lastRule.col, rule);
                     }
                 }
@@ -55,7 +56,7 @@ CSSLint.addRule({
 
             if (lastRule){
                 lastRule.propCount++;
-                if (name == "outline" && (value == "none" || value == "0")){
+                if (name === "outline" && (value.toString() === "none" || value.toString() === "0")){
                     lastRule.outline = true;
                 }
             }
diff --git a/src/rules/overqualified-elements.js b/src/rules/overqualified-elements.js
index cceb8830..13e21274 100644
--- a/src/rules/overqualified-elements.js
+++ b/src/rules/overqualified-elements.js
@@ -12,6 +12,7 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter){
+        "use strict";
         var rule = this,
             classes = {};
 
@@ -27,12 +28,12 @@ CSSLint.addRule({
 
                 for (j=0; j < selector.parts.length; j++){
                     part = selector.parts[j];
-                    if (part.type == parser.SELECTOR_PART_TYPE){
+                    if (part.type === parser.SELECTOR_PART_TYPE){
                         for (k=0; k < part.modifiers.length; k++){
                             modifier = part.modifiers[k];
-                            if (part.elementName && modifier.type == "id"){
+                            if (part.elementName && modifier.type === "id"){
                                 reporter.report("Element (" + part + ") is overqualified, just use " + modifier + " without element name.", part.line, part.col, rule);
-                            } else if (modifier.type == "class"){
+                            } else if (modifier.type === "class"){
 
                                 if (!classes[modifier]){
                                     classes[modifier] = [];
@@ -52,7 +53,7 @@ CSSLint.addRule({
                 if (classes.hasOwnProperty(prop)){
 
                     //one use means that this is overqualified
-                    if (classes[prop].length == 1 && classes[prop][0].part.elementName){
+                    if (classes[prop].length === 1 && classes[prop][0].part.elementName){
                         reporter.report("Element (" + classes[prop][0].part + ") is overqualified, just use " + classes[prop][0].modifier + " without element name.", classes[prop][0].part.line, classes[prop][0].part.col, rule);
                     }
                 }
diff --git a/src/rules/qualified-headings.js b/src/rules/qualified-headings.js
index 5000fdac..bdb46470 100644
--- a/src/rules/qualified-headings.js
+++ b/src/rules/qualified-headings.js
@@ -12,6 +12,7 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter){
+        "use strict";
         var rule = this;
 
         parser.addListener("startrule", function(event){
@@ -25,7 +26,7 @@ CSSLint.addRule({
 
                 for (j=0; j < selector.parts.length; j++){
                     part = selector.parts[j];
-                    if (part.type == parser.SELECTOR_PART_TYPE){
+                    if (part.type === parser.SELECTOR_PART_TYPE){
                         if (part.elementName && /h[1-6]/.test(part.elementName.toString()) && j > 0){
                             reporter.report("Heading (" + part.elementName + ") should not be qualified.", part.line, part.col, rule);
                         }
diff --git a/src/rules/regex-selectors.js b/src/rules/regex-selectors.js
index 030f88e1..2ab10bb3 100644
--- a/src/rules/regex-selectors.js
+++ b/src/rules/regex-selectors.js
@@ -12,6 +12,7 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter){
+        "use strict";
         var rule = this;
 
         parser.addListener("startrule", function(event){
@@ -25,10 +26,10 @@ CSSLint.addRule({
                 selector = selectors[i];
                 for (j=0; j < selector.parts.length; j++){
                     part = selector.parts[j];
-                    if (part.type == parser.SELECTOR_PART_TYPE){
+                    if (part.type === parser.SELECTOR_PART_TYPE){
                         for (k=0; k < part.modifiers.length; k++){
                             modifier = part.modifiers[k];
-                            if (modifier.type == "attribute"){
+                            if (modifier.type === "attribute"){
                                 if (/([\~\|\^\$\*]=)/.test(modifier)){
                                     reporter.report("Attribute selectors with " + RegExp.$1 + " are slow!", modifier.line, modifier.col, rule);
                                 }
diff --git a/src/rules/rules-count.js b/src/rules/rules-count.js
index 83818f6a..f2418998 100644
--- a/src/rules/rules-count.js
+++ b/src/rules/rules-count.js
@@ -12,6 +12,7 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter){
+        "use strict";
         var count = 0;
 
         //count each rule
diff --git a/src/rules/selector-max-approaching.js b/src/rules/selector-max-approaching.js
index f16da681..2cea2935 100644
--- a/src/rules/selector-max-approaching.js
+++ b/src/rules/selector-max-approaching.js
@@ -12,6 +12,7 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter) {
+        "use strict";
         var rule = this, count = 0;
 
         parser.addListener("startrule", function(event) {
diff --git a/src/rules/selector-max.js b/src/rules/selector-max.js
index d7182c29..a9892fe7 100644
--- a/src/rules/selector-max.js
+++ b/src/rules/selector-max.js
@@ -12,6 +12,7 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter){
+        "use strict";
         var rule = this, count = 0;
 
         parser.addListener("startrule", function(event) {
diff --git a/src/rules/selector-newline.js b/src/rules/selector-newline.js
index 81b9ab2f..40f8f50d 100644
--- a/src/rules/selector-newline.js
+++ b/src/rules/selector-newline.js
@@ -12,6 +12,7 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter) {
+        "use strict";
         var rule = this;
 
         parser.addListener("startrule", function(event) {
diff --git a/src/rules/shorthand.js b/src/rules/shorthand.js
index 85bbda26..2be71a86 100644
--- a/src/rules/shorthand.js
+++ b/src/rules/shorthand.js
@@ -13,6 +13,7 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter){
+        "use strict";
         var rule = this,
             prop, i, len,
             propertiesToCheck = {},
@@ -59,7 +60,7 @@ CSSLint.addRule({
                         total += properties[mapping[prop][i]] ? 1 : 0;
                     }
 
-                    if (total == mapping[prop].length){
+                    if (total === mapping[prop].length){
                         reporter.report("The properties " + mapping[prop].join(", ") + " can be replaced by " + prop + ".", event.line, event.col, rule);
                     }
                 }
diff --git a/src/rules/star-property-hack.js b/src/rules/star-property-hack.js
index 7f4f91b3..7663674f 100644
--- a/src/rules/star-property-hack.js
+++ b/src/rules/star-property-hack.js
@@ -13,13 +13,14 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter){
+        "use strict";
         var rule = this;
 
         //check if property name starts with "*"
         parser.addListener("property", function(event){
             var property = event.property;
 
-            if (property.hack == "*") {
+            if (property.hack === "*") {
                 reporter.report("Property with star prefix found.", event.property.line, event.property.col, rule);
             }
         });
diff --git a/src/rules/text-indent.js b/src/rules/text-indent.js
index 01c970f9..17536bab 100644
--- a/src/rules/text-indent.js
+++ b/src/rules/text-indent.js
@@ -13,6 +13,7 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter){
+        "use strict";
         var rule = this,
             textIndent,
             direction;
@@ -25,7 +26,7 @@ CSSLint.addRule({
 
         //event handler for end of rules
         function endRule(){
-            if (textIndent && direction != "ltr"){
+            if (textIndent && direction !== "ltr"){
                 reporter.report("Negative text-indent doesn't work well with RTL. If you use text-indent for image replacement explicitly set direction for that item to ltr.", textIndent.line, textIndent.col, rule);
             }
         }
@@ -38,9 +39,9 @@ CSSLint.addRule({
             var name = event.property.toString().toLowerCase(),
                 value = event.value;
 
-            if (name == "text-indent" && value.parts[0].value < -99){
+            if (name === "text-indent" && value.parts[0].value < -99){
                 textIndent = event.property;
-            } else if (name == "direction" && value == "ltr"){
+            } else if (name === "direction" && value.toString() === "ltr"){
                 direction = "ltr";
             }
         });
diff --git a/src/rules/underscore-property-hack.js b/src/rules/underscore-property-hack.js
index 0da1747c..de29017d 100644
--- a/src/rules/underscore-property-hack.js
+++ b/src/rules/underscore-property-hack.js
@@ -13,13 +13,14 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter){
+        "use strict";
         var rule = this;
 
         //check if property name starts with "_"
         parser.addListener("property", function(event){
             var property = event.property;
 
-            if (property.hack == "_") {
+            if (property.hack === "_") {
                 reporter.report("Property with underscore prefix found.", event.property.line, event.property.col, rule);
             }
         });
diff --git a/src/rules/unique-headings.js b/src/rules/unique-headings.js
index 22de7495..978510f2 100644
--- a/src/rules/unique-headings.js
+++ b/src/rules/unique-headings.js
@@ -12,6 +12,7 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter){
+        "use strict";
         var rule = this;
 
         var headings = {
@@ -37,7 +38,7 @@ CSSLint.addRule({
                 if (part.elementName && /(h[1-6])/i.test(part.elementName.toString())){
 
                     for (j=0; j < part.modifiers.length; j++){
-                        if (part.modifiers[j].type == "pseudo"){
+                        if (part.modifiers[j].type === "pseudo"){
                             pseudo = true;
                             break;
                         }
diff --git a/src/rules/universal-selector.js b/src/rules/universal-selector.js
index 79088986..c3fd4b9d 100644
--- a/src/rules/universal-selector.js
+++ b/src/rules/universal-selector.js
@@ -12,6 +12,7 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter){
+        "use strict";
         var rule = this;
 
         parser.addListener("startrule", function(event){
@@ -24,7 +25,7 @@ CSSLint.addRule({
                 selector = selectors[i];
 
                 part = selector.parts[selector.parts.length-1];
-                if (part.elementName == "*"){
+                if (part.elementName === "*"){
                     reporter.report(rule.desc, part.line, part.col, rule);
                 }
             }
diff --git a/src/rules/unqualified-attributes.js b/src/rules/unqualified-attributes.js
index 110fa15e..88fbd3ff 100644
--- a/src/rules/unqualified-attributes.js
+++ b/src/rules/unqualified-attributes.js
@@ -12,6 +12,7 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter){
+        "use strict";
         var rule = this;
 
         parser.addListener("startrule", function(event){
@@ -26,10 +27,10 @@ CSSLint.addRule({
                 selector = selectors[i];
 
                 part = selector.parts[selector.parts.length-1];
-                if (part.type == parser.SELECTOR_PART_TYPE){
+                if (part.type === parser.SELECTOR_PART_TYPE){
                     for (k=0; k < part.modifiers.length; k++){
                         modifier = part.modifiers[k];
-                        if (modifier.type == "attribute" && (!part.elementName || part.elementName == "*")){
+                        if (modifier.type === "attribute" && (!part.elementName || part.elementName === "*")){
                             reporter.report(rule.desc, part.line, part.col, rule);
                         }
                     }
diff --git a/src/rules/vendor-prefix.js b/src/rules/vendor-prefix.js
index d9b249ac..166ec89f 100644
--- a/src/rules/vendor-prefix.js
+++ b/src/rules/vendor-prefix.js
@@ -13,6 +13,7 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter){
+        "use strict";
         var rule = this,
             properties,
             num,
@@ -79,7 +80,7 @@ CSSLint.addRule({
         //event handler for beginning of rules
         function startRule(){
             properties = {};
-            num=1;
+            num = 1;
         }
 
         //event handler for end of rules
diff --git a/src/rules/zero-units.js b/src/rules/zero-units.js
index 08886ee8..f86e9bf0 100644
--- a/src/rules/zero-units.js
+++ b/src/rules/zero-units.js
@@ -12,6 +12,7 @@ CSSLint.addRule({
 
     //initialization
     init: function(parser, reporter){
+        "use strict";
         var rule = this;
 
         //count how many times "float" is used
@@ -21,7 +22,7 @@ CSSLint.addRule({
                 len = parts.length;
 
             while(i < len){
-                if ((parts[i].units || parts[i].type == "percentage") && parts[i].value === 0 && parts[i].type != "time"){
+                if ((parts[i].units || parts[i].type === "percentage") && parts[i].value === 0 && parts[i].type !== "time"){
                     reporter.report("Values of 0 shouldn't have units specified.", parts[i].line, parts[i].col, rule);
                 }
                 i++;
diff --git a/src/worker/Worker.js b/src/worker/Worker.js
index 7eec9f1a..f119fba6 100644
--- a/src/worker/Worker.js
+++ b/src/worker/Worker.js
@@ -4,7 +4,7 @@
 /*global self, JSON*/
 //message indicates to start linting
 self.onmessage = function(event){
-
+    "use strict";
     var data = event.data,
         message,
         text,
diff --git a/tests/all-rules.js b/tests/all-rules.js
index f6827e94..6e2956b5 100644
--- a/tests/all-rules.js
+++ b/tests/all-rules.js
@@ -11,6 +11,7 @@
 /*jshint loopfunc: true */
 
 (function(){
+    "use strict";
     var Assert = YUITest.Assert,
         suite   = new YUITest.TestSuite("General Tests for all Rules"),
         rules   = CSSLint.getRules(),
diff --git a/tests/core/CSSLint.js b/tests/core/CSSLint.js
index 300a2d25..09627707 100644
--- a/tests/core/CSSLint.js
+++ b/tests/core/CSSLint.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/core/Reporter.js b/tests/core/Reporter.js
index 8e9b99ea..6f20d6e1 100644
--- a/tests/core/Reporter.js
+++ b/tests/core/Reporter.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/formatters/checkstyle-xml.js b/tests/formatters/checkstyle-xml.js
index d069d3be..694ca81c 100644
--- a/tests/formatters/checkstyle-xml.js
+++ b/tests/formatters/checkstyle-xml.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/formatters/compact.js b/tests/formatters/compact.js
index 2f7fdd1f..78e409d0 100644
--- a/tests/formatters/compact.js
+++ b/tests/formatters/compact.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/formatters/csslint-xml.js b/tests/formatters/csslint-xml.js
index 049652a7..0a1ef617 100644
--- a/tests/formatters/csslint-xml.js
+++ b/tests/formatters/csslint-xml.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/formatters/junit-xml.js b/tests/formatters/junit-xml.js
index 21430093..49f76830 100644
--- a/tests/formatters/junit-xml.js
+++ b/tests/formatters/junit-xml.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/formatters/lint-xml.js b/tests/formatters/lint-xml.js
index 36c04919..2c940306 100644
--- a/tests/formatters/lint-xml.js
+++ b/tests/formatters/lint-xml.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/formatters/text.js b/tests/formatters/text.js
index ef41ab5b..b446ff24 100644
--- a/tests/formatters/text.js
+++ b/tests/formatters/text.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/rules/adjoining-classes.js b/tests/rules/adjoining-classes.js
index e16f2781..46eb866f 100644
--- a/tests/rules/adjoining-classes.js
+++ b/tests/rules/adjoining-classes.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/rules/box-model.js b/tests/rules/box-model.js
index 19bdcee9..a5f4b0dc 100644
--- a/tests/rules/box-model.js
+++ b/tests/rules/box-model.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/rules/box-sizing.js b/tests/rules/box-sizing.js
index 03238cc6..61e4efb0 100644
--- a/tests/rules/box-sizing.js
+++ b/tests/rules/box-sizing.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/rules/bulletproof-font-face.js b/tests/rules/bulletproof-font-face.js
index 7bb055d1..f18cbf70 100644
--- a/tests/rules/bulletproof-font-face.js
+++ b/tests/rules/bulletproof-font-face.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/rules/compatible-vendor-prefixes.js b/tests/rules/compatible-vendor-prefixes.js
index 4fec4c5b..79c008aa 100644
--- a/tests/rules/compatible-vendor-prefixes.js
+++ b/tests/rules/compatible-vendor-prefixes.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/rules/display-property-grouping.js b/tests/rules/display-property-grouping.js
index 53526c4a..be74093a 100644
--- a/tests/rules/display-property-grouping.js
+++ b/tests/rules/display-property-grouping.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/rules/duplicate-background-images.js b/tests/rules/duplicate-background-images.js
index 5eb766eb..d350ead1 100644
--- a/tests/rules/duplicate-background-images.js
+++ b/tests/rules/duplicate-background-images.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/rules/duplicate-properties.js b/tests/rules/duplicate-properties.js
index a12f4747..707de583 100644
--- a/tests/rules/duplicate-properties.js
+++ b/tests/rules/duplicate-properties.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/rules/empty-rules.js b/tests/rules/empty-rules.js
index 4b961fae..392d0eea 100644
--- a/tests/rules/empty-rules.js
+++ b/tests/rules/empty-rules.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/rules/errors.js b/tests/rules/errors.js
index 164c3832..9f667d05 100644
--- a/tests/rules/errors.js
+++ b/tests/rules/errors.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/rules/fallback-colors.js b/tests/rules/fallback-colors.js
index 6d964db6..2797ab05 100644
--- a/tests/rules/fallback-colors.js
+++ b/tests/rules/fallback-colors.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/rules/floats.js b/tests/rules/floats.js
index fd78db3b..7150becd 100644
--- a/tests/rules/floats.js
+++ b/tests/rules/floats.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/rules/font-faces.js b/tests/rules/font-faces.js
index 2fd4660b..14000594 100644
--- a/tests/rules/font-faces.js
+++ b/tests/rules/font-faces.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/rules/font-sizes.js b/tests/rules/font-sizes.js
index c5831103..0f53ed17 100644
--- a/tests/rules/font-sizes.js
+++ b/tests/rules/font-sizes.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/rules/gradients.js b/tests/rules/gradients.js
index 69e80362..cabfd384 100644
--- a/tests/rules/gradients.js
+++ b/tests/rules/gradients.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/rules/ids.js b/tests/rules/ids.js
index 9f309b26..1c710896 100644
--- a/tests/rules/ids.js
+++ b/tests/rules/ids.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/rules/import.js b/tests/rules/import.js
index 967dc207..574b5d30 100644
--- a/tests/rules/import.js
+++ b/tests/rules/import.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/rules/important.js b/tests/rules/important.js
index 5d4ff1af..ef10ce9f 100644
--- a/tests/rules/important.js
+++ b/tests/rules/important.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/rules/known-properties.js b/tests/rules/known-properties.js
index f35b11a9..2e4fd44e 100644
--- a/tests/rules/known-properties.js
+++ b/tests/rules/known-properties.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/rules/order-alphabetical.js b/tests/rules/order-alphabetical.js
index 551c8e2a..abab0b48 100644
--- a/tests/rules/order-alphabetical.js
+++ b/tests/rules/order-alphabetical.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/rules/outline-none.js b/tests/rules/outline-none.js
index d4501d16..d8d87902 100644
--- a/tests/rules/outline-none.js
+++ b/tests/rules/outline-none.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/rules/overqualified-elements.js b/tests/rules/overqualified-elements.js
index 54b1a009..368fcaee 100644
--- a/tests/rules/overqualified-elements.js
+++ b/tests/rules/overqualified-elements.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/rules/qualified-headings.js b/tests/rules/qualified-headings.js
index 403df290..0ee85ecd 100644
--- a/tests/rules/qualified-headings.js
+++ b/tests/rules/qualified-headings.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/rules/regex-selectors.js b/tests/rules/regex-selectors.js
index 1e3c8d5f..a7ce67bd 100644
--- a/tests/rules/regex-selectors.js
+++ b/tests/rules/regex-selectors.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/rules/selector-max-approaching.js b/tests/rules/selector-max-approaching.js
index f47e6072..701fea89 100644
--- a/tests/rules/selector-max-approaching.js
+++ b/tests/rules/selector-max-approaching.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert, i, j, css1 = "", css2 = "", css3 = "", css4 = "";
 
     // create css1, which has only 4095 rules and 4095 selectors
diff --git a/tests/rules/selector-max.js b/tests/rules/selector-max.js
index 02cb824f..57092d5a 100644
--- a/tests/rules/selector-max.js
+++ b/tests/rules/selector-max.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert, i, j, css1 = "", css2 = "", css3 = "", css4 = "";
 
     // create css1, which has only 4095 rules and 4095 selectors
diff --git a/tests/rules/selector-newline.js b/tests/rules/selector-newline.js
index e22f2e3e..42e2f9e7 100644
--- a/tests/rules/selector-newline.js
+++ b/tests/rules/selector-newline.js
@@ -1,5 +1,5 @@
 (function () {
-
+    "use strict";
     var ruleId = "selector-newline", expectWarning, expectPass;
 
     expectWarning = function (ruleset, expectedMessage) {
diff --git a/tests/rules/shorthand.js b/tests/rules/shorthand.js
index ca582048..17d51f8e 100644
--- a/tests/rules/shorthand.js
+++ b/tests/rules/shorthand.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/rules/star-property-hack.js b/tests/rules/star-property-hack.js
index 433cc022..20c5c3c3 100644
--- a/tests/rules/star-property-hack.js
+++ b/tests/rules/star-property-hack.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/rules/text-indent.js b/tests/rules/text-indent.js
index ff8e0617..d2b17e83 100644
--- a/tests/rules/text-indent.js
+++ b/tests/rules/text-indent.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/rules/underscore-property-hack.js b/tests/rules/underscore-property-hack.js
index ee9efaf7..b4e4107d 100644
--- a/tests/rules/underscore-property-hack.js
+++ b/tests/rules/underscore-property-hack.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/rules/unique-headings.js b/tests/rules/unique-headings.js
index 3a251cc6..7999c4de 100644
--- a/tests/rules/unique-headings.js
+++ b/tests/rules/unique-headings.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/rules/universal-selector.js b/tests/rules/universal-selector.js
index 7adbf865..3e3874db 100644
--- a/tests/rules/universal-selector.js
+++ b/tests/rules/universal-selector.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/rules/unqualified-attributes.js b/tests/rules/unqualified-attributes.js
index 1159f64e..0042c712 100644
--- a/tests/rules/unqualified-attributes.js
+++ b/tests/rules/unqualified-attributes.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/rules/vendor-prefix.js b/tests/rules/vendor-prefix.js
index d5aa83c0..9ec09aed 100644
--- a/tests/rules/vendor-prefix.js
+++ b/tests/rules/vendor-prefix.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/rules/zero-units.js b/tests/rules/zero-units.js
index d1b583cd..1ac4797e 100644
--- a/tests/rules/zero-units.js
+++ b/tests/rules/zero-units.js
@@ -1,4 +1,5 @@
 (function(){
+    "use strict";
     var Assert = YUITest.Assert;
 
     YUITest.TestRunner.add(new YUITest.TestCase({
diff --git a/tests/testrunner.htm b/tests/testrunner.htm
index 49fe61c8..37d598b8 100644
--- a/tests/testrunner.htm
+++ b/tests/testrunner.htm
@@ -28,6 +28,7 @@ <h2>Results</h2>
 
     <script >
         (function(){
+            "use strict";
 
             //some helpful variables
             var runButton   = document.getElementById("run"),