Update examples

Author: mdmintz

examples/offline_examples/demo_page.html

@@ -441,7 +441,7 @@ <h4>iFrame%20Text<%2Fh4></body>"></iframe>
 
                         <td>
                             <a id="myLink4" name="linkName4" class="linkClass"
-                               href="https://seleniumbase.io/demo_page.html">
+                               href="https://seleniumbase.io/demo_page/">
                                SeleniumBase Demo Page</a>
                         </td>
                     </tr>

examples/test_demo_site.py

@@ -4,7 +4,7 @@
 class MyTestClass(BaseCase):
 
     def test_demo_site(self):
-        self.open("https://seleniumbase.io/demo_page.html")
+        self.open("https://seleniumbase.io/demo_page/")
 
         # Assert the title of the current web page
         self.assert_title("Web Testing Page")

examples/test_error_page.py

@@ -0,0 +1,17 @@
+""" Test an error page with the "highlight() command, which uses a
+    JavaScript animation to point out page objects that are found.
+    If an element isn't visible, the test fails with an exception.
+"""
+from seleniumbase import BaseCase
+
+
+class MyTestClass(BaseCase):
+
+    def test_error_page(self):
+        self.open("https://seleniumbase.io/error_page/")
+        self.highlight('img[alt="500 Error"]')
+        self.highlight("img#parallax_octocat")
+        self.highlight("#parallax_error_text")
+        self.highlight('img[alt*="404"]')
+        self.highlight("img#octobi_wan_catnobi")
+        self.highlight("img#speeder")