function fenster(winname,wintitel,breite,hoehe) {
	var links=screen.width/2-breite/2;
	var oben=screen.height/2-hoehe/2;
	NewWin = window.open(winname, wintitel, "width="+breite+",height="+hoehe+",top="+oben+",left="+links+",toolbar=0,scrollbars=yes,location=0");
}