Sys.WebForms.PageRequestManager.getInstance().add_beginRequest(BeginRequestHandler);
    Sys.WebForms.PageRequestManager.getInstance().add_endRequest(EndRequestHandler);

    var elem = null;
    var value = "";
    var width = "";
    var height = "";
    var borderWidth = "";
    var backgroundcolor = "";
    function BeginRequestHandler(sender, args) {
        elem = args.get_postBackElement();
        value = elem.value;
        width = document.getElementById(elem.id).style.width;
        height = document.getElementById(elem.id).style.height;
        borderWidth = document.getElementById(elem.id).style.borderWidth;
        backgroundcolor = document.getElementById(elem.id).style.backgroundColor;
        document.getElementById(elem.id).value = "";
        document.getElementById(elem.id).style.backgroundImage = "url(Images/loading5.gif)";
        document.getElementById(elem.id).disabled = true;
        document.getElementById(elem.id).style.borderWidth = 0;
        document.getElementById(elem.id).style.width = 22 + "px";
        document.getElementById(elem.id).style.height = 22 + "px";
        document.getElementById(elem.id).style.backgroundColor = "Transparent";
    }
    function EndRequestHandler(sender, args) {
        document.getElementById(elem.id).disabled = false;
        document.getElementById(elem.id).value = value;
        document.getElementById(elem.id).style.backgroundImage = "";
        document.getElementById(elem.id).style.borderWidth = borderWidth;
        document.getElementById(elem.id).style.width = width;
        document.getElementById(elem.id).style.height = height;
        document.getElementById(elem.id).style.backgroundColor = backgroundcolor;
    }