function unloadSWF(){
getFlashMovie('zenonclient').removeZC("");     
}

function getFlashMovie(movieName) {
   var isIE = navigator.appName.indexOf("Microsoft") != -1;   
return (isIE) ? window[movieName] : document[movieName];  
} 

function init(){
window['g_bPreventUnload'] = false;
if (window.attachEvent){
window.attachEvent("onunload", unloadSWF);
}else{
window.onbeforeunload = unloadSWF;
} 
}

window.onload = init;