function openwindow(mypage, w, h) 
{
    var winl = (screen.width - w) / 2;
    var wint = (screen.height - h) / 2;
    winprops = 'height='+h+',width='+w+',top='+wint+',left='+winl+',scrollbars,resizable'
    win = window.open(mypage, 'tmp', winprops)
    if (parseInt(navigator.appVersion) >= 4) { win.window.focus(); }
}