try this one

< script type="text/javascript">
var prm = Sys.WebForms.PageRequestManager.getInstance();
prm.add_pageLoaded(pageLoaded);
var c = 0;
function pageLoaded(sender, args)
{
var img = document.getElementById("Control");
c++;
img.src = img.src + "?" + c;
}

plz mark as ANSWER if it helps u