function centerPopup(url,width,height,name) {
  var str="height="+height+",innerHeight="+height;
  str+=",width="+width+",innerWidth="+width;
  if (window.screen) {
    var ah=screen.availHeight-30;
    var aw=screen.availWidth-10;

    var xc=(aw-width)/2;
    var yc=(ah-height)/2;

    str+=",left="+xc+",screenX="+xc;
    str+=",top="+yc+",screenY="+yc;
  }
  str+=",scrollbars=yes";
  str+=",resizable=yes";
  str+=",toolbar=no";
  return window.open(url,name,str);
}