Index: /CKEditor/trunk/_source/core/env.js
===================================================================
--- /CKEditor/trunk/_source/core/env.js	(revision 6586)
+++ /CKEditor/trunk/_source/core/env.js	(revision 6587)
@@ -145,4 +145,14 @@
 			 */
 			env.ie8Compat = document.documentMode == 8;
+
+			/**
+			 * Indicates that CKEditor is running on Internet Explorer 9's standards mode.
+			 * @name CKEDITOR.env.ie9Compat
+			 * @type Boolean
+			 * @example
+			 * if ( CKEDITOR.env.ie9Compat )
+			 *     alert( "IE9, the beauty of the web!" );
+			 */
+			env.ie9Compat = document.documentMode == 9;
 
 			/**