Fire Javascript event while closing chrome browser

Hi All,

I tried many ways to fire the event while closing the chrome browser since my application got some security issues due to the new option "Continue where is left off"

$(window).unload(function () {

    if (event.clientY < 0) {

        alert("123");

    }

noting get worked except the below but my custom event not getting fired to clear the session cookie

window.onbeforeunload = check;

function check()

{

return "Are you sure you want to exit this page?";

//or put whatever function you need to call when a user closes the web //browser.

}

Please any one tell me the idea to clear session cookie by a program.

Thanks