setTimeout("AddPageRequestManagerEventHandlers()", 1000);

function AddPageRequestManagerEventHandlers()
{
    if (typeof(Sys) != "undefined")
    {
        FocusedElementID = "";
        Sys.WebForms.PageRequestManager.getInstance().add_pageLoading(FindFocusedElement);
        Sys.WebForms.PageRequestManager.getInstance().add_pageLoaded(FocusElementAfterUpdating);
    }
}

function FindFocusedElement(sender, args) 
{
	FocusedElementID = document.activeElement ? document.activeElement.id : "";
}

function FocusElementAfterUpdating(sender, args) 
{
   setTimeout("FocusElementIfNotAnyFocused()", 100);
}

function FocusElementIfNotAnyFocused()
{
    var elem = FocusedElementID != "" ? document.getElementById(FocusedElementID) : null;
    if (elem && elem.focus && elem.tagName != "IFRAME")
        elem.focus();
        
    FocusedElementID = "";
}