function openstart()
    {
    var breite = 700;
    var hoehe = 585;
    var posX=(screen.availWidth-breite)/2;
    var posY=(screen.availHeight-hoehe)/2;

    window.open('impressionen.htm',"","toolbar=no,width=700,height=585,directories=no,status=no,scrollbars=no,resize=no,resizable=no,menubar=no,screenX=" + posX + ",screenY=" + posY + ",left=" + posX + ",top=" + posY + "");
	}