var fenster;
function gfx2_opener(url){
	var top, left, width=800, height=600;
	top  = Math.round((screen.height - height)/2);
	left = Math.round((screen.width - width)/2);

	if(fenster){
		fenster.close();
	}

	fenster = window.open(url, 'Meldung', 'width='+width+',height='+height+',left='+left+',top='+top+',scrollbars=yes, status=yes');
	fenster.focus();
}