Index: /CKEditor/trunk/_source/plugins/wysiwygarea/plugin.js
===================================================================
--- /CKEditor/trunk/_source/plugins/wysiwygarea/plugin.js	(revision 5241)
+++ /CKEditor/trunk/_source/plugins/wysiwygarea/plugin.js	(revision 5242)
@@ -278,9 +278,5 @@
 							( isCustomDomain ? ( 'document.domain="' + document.domain + '";' ) : '' ) +
 
-							// With FF, it's better to load the data on
-							// iframe.load. (#3894,#4058)
-							// But in FF, we still need the open()-close() call
-							// to avoid HTTPS warnings.
-							( CKEDITOR.env.gecko ? '' : ( 'parent.CKEDITOR.tools.callFunction(' + setDataFn + ',document);' ) ) +
+							( ( 'parent.CKEDITOR.tools.callFunction(' + setDataFn + ',document);' ) ) +
 
 							'document.close();';
@@ -289,6 +285,8 @@
   							' style="width:100%;height:100%"' +
   							' frameBorder="0"' +
-  							' src="javascript:void(function(){' + encodeURIComponent( srcScript ) + '}())"' +
-  							' tabIndex="' + editor.tabIndex + '"' +
+							// With FF, the 'src' attribute should be left empty to
+							// trigger iframe's 'load' event.
+  							' src="' + ( CKEDITOR.env.gecko ? '' : 'javascript:void(function(){' + encodeURIComponent( srcScript ) + '}())' ) + '"' +
+							' tabIndex="' + editor.tabIndex + '"' +
   							' allowTransparency="true"' +
   							'></iframe>' );