Close Tab and Browser Issue ?

Question

 

I will browser click then show this popup . But here i will face a problem . I will click reload button and cancel button but same work those all button . I want to delete data only Reload button. 

window.onbeforeunload = function (e,f) {

e = e || window.event;

//f = window.event;

// For IE and Firefox prior to version 4

if (e) {

e.returnValue = AjaxCall();

}

// For Safari

return 'Any string';

};

This my code . Please solve this issue.