var Fenster = null;
function openWindow(meineSeite,meinName){

    w = 640;
    h = 480;

    LeftPosition = (screen.width) ? (screen.width-w)/2 : 0;
    TopPosition = (screen.height) ? (screen.height-h)/2 : 0;

    settings ='height='+h+',width='+w+',top='+TopPosition+',left='+LeftPosition+',scrollbars=0,resizable'

    Fenster = window.open(meineSeite,meinName,settings)
}

function closeWindow() {
    window.close();
}