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