Index: _source/core/dom/element.js
===================================================================
--- _source/core/dom/element.js	(revision 5799)
+++ _source/core/dom/element.js	(working copy)
@@ -789,7 +789,7 @@
 			{
 				var child = children.getItem( i );
 
-				if ( child.type == CKEDITOR.NODE_ELEMENT && child.getAttribute( '_fck_bookmark' ) )
+				if ( child.type == CKEDITOR.NODE_ELEMENT && child.getAttribute( '_cke_bookmark' ) )
 					continue;
 
 				if ( child.type == CKEDITOR.NODE_ELEMENT && !child.isEmptyInlineRemoveable()
@@ -917,7 +917,7 @@
 					// queuing them to be moved later. (#5567)
 					var pendingNodes = [];
 
-					while ( sibling.getAttribute( '_fck_bookmark' )
+					while ( sibling.getAttribute( '_cke_bookmark' )
 						|| sibling.isEmptyInlineRemoveable() )
 					{
 						pendingNodes.push( sibling );
Index: _source/core/dom/range.js
===================================================================
--- _source/core/dom/range.js	(revision 5799)
+++ _source/core/dom/range.js	(working copy)
@@ -305,7 +305,7 @@
 		return node.type != CKEDITOR.NODE_TEXT
 			    && node.getName() in CKEDITOR.dtd.$removeEmpty
 			    || !CKEDITOR.tools.trim( node.getText() )
-			    || node.getParent().hasAttribute( '_fck_bookmark' );
+			    || node.getParent().hasAttribute( '_cke_bookmark' );
 	}
 
 	var whitespaceEval = new CKEDITOR.dom.walker.whitespaces(),
@@ -399,7 +399,7 @@
 			var clone;
 
 			startNode = this.document.createElement( 'span' );
-			startNode.setAttribute( '_fck_bookmark', 1 );
+			startNode.setAttribute( '_cke_bookmark', 1 );
 			startNode.setStyle( 'display', 'none' );
 
 			// For IE, it must have something inside, otherwise it may be
@@ -705,10 +705,10 @@
 				endNode = this.endContainer;
 
 			if ( startNode.is && startNode.is( 'span' )
-				&& startNode.hasAttribute( '_fck_bookmark' ) )
+				&& startNode.hasAttribute( '_cke_bookmark' ) )
 				this.setStartAt( startNode, CKEDITOR.POSITION_BEFORE_START );
 			if ( endNode && endNode.is && endNode.is( 'span' )
-				&& endNode.hasAttribute( '_fck_bookmark' ) )
+				&& endNode.hasAttribute( '_cke_bookmark' ) )
 				this.setEndAt( endNode,  CKEDITOR.POSITION_AFTER_END );
 		},
 
@@ -914,7 +914,7 @@
 								// If this is a visible element.
 								// We need to check for the bookmark attribute because IE insists on
 								// rendering the display:none nodes we use for bookmarks. (#3363)
-								if ( sibling.$.offsetWidth > 0 && !sibling.getAttribute( '_fck_bookmark' ) )
+								if ( sibling.$.offsetWidth > 0 && !sibling.getAttribute( '_cke_bookmark' ) )
 								{
 									// We'll accept it only if we need
 									// whitespace, and this is an inline
@@ -1073,7 +1073,7 @@
 								// If this is a visible element.
 								// We need to check for the bookmark attribute because IE insists on
 								// rendering the display:none nodes we use for bookmarks. (#3363)
-								if ( sibling.$.offsetWidth > 0 && !sibling.getAttribute( '_fck_bookmark' ) )
+								if ( sibling.$.offsetWidth > 0 && !sibling.getAttribute( '_cke_bookmark' ) )
 								{
 									// We'll accept it only if we need
 									// whitespace, and this is an inline
Index: _source/core/dom/walker.js
===================================================================
--- _source/core/dom/walker.js	(revision 5799)
+++ _source/core/dom/walker.js	(working copy)
@@ -374,7 +374,7 @@
 		{
 			return ( node && node.getName
 					&& node.getName() == 'span'
-					&& node.hasAttribute('_fck_bookmark') );
+					&& node.hasAttribute('_cke_bookmark') );
 		}
 
 		return function( node )
Index: _source/plugins/styles/plugin.js
===================================================================
--- _source/plugins/styles/plugin.js	(revision 5799)
+++ _source/plugins/styles/plugin.js	(working copy)
@@ -407,7 +407,7 @@
 				var nodeType = currentNode.type;
 				var nodeName = nodeType == CKEDITOR.NODE_ELEMENT ? currentNode.getName() : null;
 
-				if ( nodeName && currentNode.getAttribute( '_fck_bookmark' ) )
+				if ( nodeName && currentNode.getAttribute( '_cke_bookmark' ) )
 				{
 					currentNode = currentNode.getNextSourceNode( true );
 					continue;
@@ -813,7 +813,7 @@
 	{
 		// Exclude the ones at header OR at tail,
 		// and ignore bookmark content between them.
-		var duoBrRegex = /(\S\s*)\n(?:\s|(<span[^>]+_fck_bookmark.*?\/span>))*\n(?!$)/gi,
+		var duoBrRegex = /(\S\s*)\n(?:\s|(<span[^>]+_cke_bookmark.*?\/span>))*\n(?!$)/gi,
 			blockName = preBlock.getName(),
 			splitedHtml = replace( preBlock.getOuterHtml(),
 				duoBrRegex,
@@ -835,7 +835,7 @@
 		var headBookmark = '',
 			tailBookmark = '';
 
-		str = str.replace( /(^<span[^>]+_fck_bookmark.*?\/span>)|(<span[^>]+_fck_bookmark.*?\/span>$)/gi,
+		str = str.replace( /(^<span[^>]+_cke_bookmark.*?\/span>)|(<span[^>]+_cke_bookmark.*?\/span>$)/gi,
 			function( str, m1, m2 ){
 					m1 && ( headBookmark = m1 );
 					m2 && ( tailBookmark = m2 );