I found the mwCustomEditButtons in wikipedia's "mediawiki:monobook.js" which is designed to add edit tool buttons above edit box. However, in my wiki, a javascript error ocurred when I try to do the same thing. I wonder where the mwCustomEditButtons be difined.

here is code from "mediawiki:monobook.js" in wikipedia:

/* add a redirect button to the edit page toolbar */ if (mwCustomEditButtons) { mwCustomEditButtons[mwCustomEditButtons.length] = { "imageFile": "http://upload.wikimedia.org/wikipedia/en/c/c8/Button_redirect.png", "speedTip": "Redirect", "tagOpen": "#REDIRECT [[", "tagClose": "]]", "sampleText": "Insert text"}; };

/*