[removed] and [removed] is not working in Firefox , Safari , Opera?

Question

In my chat application I need to get confirmation from user , when my application closes.

So I used the window.onbeforeunload for confirmation alert and

Answer 1

I got the solution for onunload in all browsers except Opera by changing the Ajax asynchronous request into synchronous request.

xmlhttp.open("POST","LogoutAction",false);

It works well for all browsers except Opera.