<window xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"> <script> function boom() { var a = document.getElementById("a"); while (a.firstChild) a.removeChild(a.firstChild); } window.addEventListener("load", boom, false); </script> <menulist id="a" sizetopopup="pref"><menupopup/><menupopup/></menulist> </window>