About closing browser exit system experience and methods of clearing session

1, first page Add the following code window.onbeforeunload = function (evt) {var evt = (evt)? evt:window.event;
if ($.browser.msie) {
Evt.cancelbubble = true;
Return "Are you sure you want to exit the system? ";
else if ($.browser.mozilla!= undefined) {
Evt.stoppropagation ();
var result = confirm ("Are you sure you want to exit the system?") ");
if (!result) {
return false;
} else {
Window.onunload = unload;
}
}
}
Window.onunload = function (evt) {
var evt = (evt)? Evt:window.event;
if ($.browser.mozilla!= undefined) {//Firefox clears this event to prevent bubbling
Window.onbeforeunload = function () {}
}
window.open ("/account/logoff/");
Window.opener = null; Window.close ();
//define two global variables that can be restored after the event is cleared.
var beforeunload = window.onbeforeunload;
var unload = window.onunload;     2, the page of a label "href" Set to "#", if there is a link, please use onclick.     3, if there are methods on the page to call Location.href, please clear two events before setting, or directly set to NULL. 4, if there are methods in the page to dynamically load IFRAME, please clear two events before loading, after loading completed, and then restore two events.