function openPopUp(url,winwidth,winheight) {
	// calculate top/left positioning
	var winl = (screen.width - winwidth) / 2;
	var wint = (screen.height - winheight) / 2;
	// open sized and centered window
	window.open(url,'Worsley','width='+winwidth+',height='+winheight+',top='+wint+',left='+winl+',toolbar=0,scrollbars=0,location=0,statusbar=0,menubar=0,resizable=0');
	// end function
	return;
	}