I'm not sure if it's what you are looking for.. put this part in head section
PHP Code:
<SCRIPT LANGUAGE="JavaScript">
var exit=true;
function unload() {
if (exit){
window.open('YOURURL');
}
}
// -->
</SCRIPT>
than execute this function on window exit by adding
PHP Code:
<body OnBeforeUnload="unload()">
you can also put this line at each <a href >if you want your exit window appear only if someone doesn't click any link
PHP Code:
target="_self" onClick="exit=false"
however if you are trying to flood your users with popups most likely they will try to quit this hell rather than spend some money