onbefore unload not working in firefox

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Javascript

HTML

Firefox

IE8

chrome

<script type="text/javascript">
        var sessionID = getQuerystring('SessionID');
        var cookieSessionID = getCookie('session');
        var validNavigation = false;

        function endSession() {
            setCookie('session', sessionID, 1);
            var cookieSU = getCookie('session');
            if (cookieSU != null) {
                getSyncData('strSessionId=' + sessionID, 'UpdateUserLogoutSession');
            }
        }

        function wireUpEvents() {
            window.onbeforeunload = function () {
                if (!validNavigation) {
                    endSession();
                }
            }


            $('document').bind('keypress', function (e) {
                if (e.keyCode == 116) {
                    validNavigation = true;
                }
            });

            $("a").bind("click", function () {
                validNavigation = true;
            });

            $("form").bind("submit", function () {
                validNavigation = true;
            });

            $("input[type=submit]").bind("click", function () {
                validNavigation = true;
            });

        }

        $(document).ready(function () {
            if (cookieSessionID == null || cookieSessionID != sessionID) {
                // Do nothing
            } else {
                if (cookieSessionID == sessionID) {
                    getData('strSessionId=' + sessionID, 'UpdateUserResetSession', function (result) {
                        if (result['Exception']) { };
                    });
                }
            }
            wireUpEvents();
        });

        function setCookie(c_name, value, exdays) {
            var exdate = new Date();
            exdate.setDate(exdate.getDate() + exdays);
            var c_value = escape(value) + ((exdays == null) ? "" : "; expires=" + exdate.toUTCString());
            document.cookie = c_name + "=" + c_value;
        }
        function getCookie(c_name) {
            var i, x, y, ARRcookies = document.cookie.split(";");
            for (i = 0; i < ARRcookies.length; i++) {
                x = ARRcookies[i].substr(0, ARRcookies[i].indexOf("="));
                y = ARRcookies[i].substr(ARRcookies[i].indexOf("=") + 1);
                x = x.replace(/^\s+|\s+$/g, "");
                if (x == c_name) {
                    return unescape(y);
                }
            }
        }
    </script>

Hey guys here i am calling

UpdateUserLogoutSession

in

window.onbeforeunload

event...
Now the problem is this works great on IE and Chrome..but it doesnt work on Firefox browser...
This function identify whether the page is REFRESHED or Closed........
So i want to use

UpdateUserResetSession 

on Refresh event and

UpdateUserLogoutSession

on close..!

Is there a way to do this in Firefox?
And Why it is not working?
One more thing....if i put

alert("hi");

after

setCookie('session', sessionID, 1);
            var cookieSU = getCookie('session');
            if (cookieSU != null) {
                getSyncData('strSessionId=' + sessionID, 'UpdateUserLogoutSession');
            }

it just works great..but when i try without alert..it doesnt work?

Whats the problem?