Index: /CKEditor/trunk/CHANGES.html
===================================================================
--- /CKEditor/trunk/CHANGES.html	(revision 4725)
+++ /CKEditor/trunk/CHANGES.html	(revision 4726)
@@ -100,4 +100,5 @@
 		<li><a href="http://dev.fckeditor.net/ticket/4521">#4521</a> : Fixed dialog layout in IE6/7 may have scroll-bar and other weird effects.</li>
 		<li><a href="http://dev.fckeditor.net/ticket/4709">#4709</a> : Fixed inconsistent scroll-bar behavior on IE.</li>
+		<li><a href="http://dev.fckeditor.net/ticket/4776">#4776</a> : Fixed preview page failed to open when relative URl contains in document.</li>
 		<li>Updated the following language files:<ul>
 			<li><a href="http://dev.fckeditor.net/ticket/4346">#4346</a> : Dutch;</li>
Index: /CKEditor/trunk/_source/plugins/preview/plugin.js
===================================================================
--- /CKEditor/trunk/_source/plugins/preview/plugin.js	(revision 4725)
+++ /CKEditor/trunk/_source/plugins/preview/plugin.js	(revision 4726)
@@ -76,4 +76,5 @@
 			if ( !isCustomDomain )
 			{
+				oWindow.document.open();
 				oWindow.document.write( sHTML );
 				oWindow.document.close();