//open frameset window for Tutorial Exercise
function popExFs(url) {
	var width = parseInt(screen.availWidth * .9);
	if (width < 760 ) {width=760;}
	if (width > 980 ) {width=980;}
	var height = parseInt(screen.availHeight * .9);
	var params = 'width='+width+',height='+height+',menubar=no,toolbar=no,location=no,directories=no,fullscreen=no,titlebar=no,hotkeys=no,status=yes,scrollbars=yes,resizable=yes,top=0,left=0'; //no spaces between elements
	popup=window.open(url,'Exercise',params);
	// calls to window.open with the same window name as an already existing window ('Exercise') , loads the URL into that window and gives a reference to the window back (popup). The window isn't given focus, its opener property isn't changed, and a third argument to window.open is ignored. 
	popup.focus(); //bring to front
	return false;
};