[css-backgrounds-4][css-borders-4][editorial] Fixed indentation and a bunch of Bikeshed issues (#9594)

Author: SebastianZ

css-backgrounds-4/Overview.bs

@@ -18,6 +18,7 @@ Warning: Not Ready
 <pre class="link-defaults">
 spec:css-text-4; type:value; text:collapse
 spec:css-shapes-2; type:function; text:path()
+spec:css-borders-4; type:property; text:border-color
 </pre>
 
 <link rel="stylesheet" href="style.css" />
@@ -100,7 +101,7 @@ Background Positioning Longhands: the 'background-position-x', 'background-posit
 	</pre>
 
 	This property specifies the background position's horizontal component.
-	An omitted origin keyword is assumed to be ''left''.
+	An omitted origin keyword is assumed to be ''background-position-x/left''.
 
 	<pre class="propdef">
 		Name: background-position-y
@@ -114,7 +115,7 @@ Background Positioning Longhands: the 'background-position-x', 'background-posit
 	</pre>
 
 	This property specifies the background position's vertical component.
-	An omitted origin keyword is assumed to be ''top''.
+	An omitted origin keyword is assumed to be ''background-position-y/top''.
 
 	<pre class="propdef">
 		Name: background-position-inline
@@ -254,7 +255,8 @@ Additions since [[CSS3BG]]</h3>
 	* added 'background-clip'
 	* added 'background-tbd'
 
-<h2 id="acknowledgments">Acknowledgments</h2>
+<h2 id="acknowledgments">
+Acknowledgments</h2>
 
 	<p>In addition to the many contributors to the [[CSS1]], [[CSS21]],
 	and [[CSS3BG]] predecessors to this module,