Sys.Application.add_load(ApplicationLoadHandler)
function ApplicationLoadHandler(sender, args)
{
    Sys.WebForms.PageRequestManager.getInstance().add_beginRequest(beginRequest);
    Sys.WebForms.PageRequestManager.getInstance().add_endRequest(endRequest);
}
function beginRequest(sender, args)
{
    var divProgress = $get('divProgress');

    if (divProgress != null)
    {
        divProgress.style.display = '';
    }
}
function endRequest(visString, msg)
{
    var divProgress = $get('divProgress');

    if (divProgress != null)
    {
        divProgress.style.display = 'none';
    }
}