<!DOCTYPE html>
<html>
<head>
</head>
<body>
</body>
<script>
window.onbeforeunload=function(e){
return 'foo';
}
</script>
</html>
<!DOCTYPE html>
<html>
<head>
</head>
<body>
</body>
<script>
window.onbeforeunload=function(e){
return 'foo';
}
</script>
</html>