Hi Marius, I have change it to $wnd["wysiwyg_editor"], so now it looks like: native void setBackgroudColor(String color) /*-{ $wnd["wysiwyg_editor"].getCommandManager().execute('backcolor', color); alert($wnd["wysiwyg_editor"].getCommandManager().getValue('backcolor')); }-*/; And this time the error says:"$wnd[ab].getCommandManager is not a function" Please see the screenshot: http://picasaweb.google.com/lh/photo/wLOJbhbvl0xZe1ZWshA5wg?feat=directlink I was wondering is it because the Java code setBackgroudColor("yellow"); and in native JavaScript do not accept double quoted string only single quoted string? I do deleted all xwiki web 2.0 jar files in lib and replaced with 2.02 jar files. I have no idea what went wrong. Any advise? Thank you, Marius! -Leon