function fenster_mitte(src,name,ww,wh)
{
    if(window.open) {
            h=screen.availHeight;
			w=screen.availWidth;
			wt=Math.floor((h-wh)/2);
			wl=Math.floor((w-ww)/2);
			                    newwin=window.open(src,name,"toolbar=no,location=no,directories=no,status=no,menubar=no,scrollbars=yes,top="+wt+",left="+wl+",height="+wh+", width="+ww+", resizable=no, copyhistory=no");
            newwin.focus();
    }
}