Index: /CKEditor/trunk/CHANGES.html
===================================================================
--- /CKEditor/trunk/CHANGES.html	(revision 4541)
+++ /CKEditor/trunk/CHANGES.html	(revision 4542)
@@ -80,4 +80,5 @@
 		<li><a href="http://dev.fckeditor.net/ticket/4073">#4073</a> : Fixed insert template with replace option could result in empty document.</li>
 		<li><a href="http://dev.fckeditor.net/ticket/4455">#4455</a> : Fixed unable to start editing when image inside document not loaded.</li>
+		<li><a href="http://dev.fckeditor.net/ticket/4517">#4517</a> : Fixed 'dialog_backgroundCoverColor' doesn't work on IE6.</li>
 	<h3>
 		CKEditor 3.0.1</h3>
Index: /CKEditor/trunk/_source/plugins/dialog/plugin.js
===================================================================
--- /CKEditor/trunk/_source/plugins/dialog/plugin.js	(revision 4541)
+++ /CKEditor/trunk/_source/plugins/dialog/plugin.js	(revision 4542)
@@ -1681,9 +1681,11 @@
 		if ( !coverElement )
 		{
+			var backgroundColorStyle = editor.config.dialog_backgroundCoverColor || 'white';
+
 			var html = [
 					'<div style="position: ', ( CKEDITOR.env.ie6Compat ? 'absolute' : 'fixed' ),
 					'; z-index: ', editor.config.baseFloatZIndex,
 					'; top: 0px; left: 0px; ',
-					'background-color: ', editor.config.dialog_backgroundCoverColor || 'white',
+					( !CKEDITOR.env.ie6Compat ? 'background-color: ' + backgroundColorStyle : '' ),
 					'" id="cke_dialog_background_cover">'
 				];
@@ -1693,5 +1695,6 @@
 			{
 				// Support for custom document.domain in IE.
-				var isCustomDomain = CKEDITOR.env.isCustomDomain();
+				var isCustomDomain = CKEDITOR.env.isCustomDomain(),
+					iframeHtml = '<html><body style=\\\'background-color:' + backgroundColorStyle + ';\\\'></body></html>';
 
 				html.push(
@@ -1702,13 +1705,10 @@
 						' src="javascript:' );
 
-				html.push(
-						isCustomDomain ?
-							'void((function(){' +
+				html.push( 'void((function(){' +
 								'document.open();' +
-								'document.domain=\'' + document.domain + '\';' +
+								( isCustomDomain ? 'document.domain=\'' + document.domain + '\';' : '' ) +
+								'document.write( \'' + iframeHtml + '\' );' +
 								'document.close();' +
-							'})())'
-						:
-							'\'\'' );
+							'})())' );
 
 				html.push(
