function mapWindow(url, windowName, windowHeight, windowWidth){

  var winwidth      = windowWidth;
  var winheight     = windowHeight;
  var desktopHeight = screen.availHeight;
  var desktopWidth  = screen.availWidth; 

  var top   = (desktopHeight - winheight) / 2;
  var left  = (desktopWidth - winwidth) / 2;

  var urlPrefix = "";
  var winurl    = url;

  var winname   = windowName;
  var winopt    = "toolbar=0,location=0,directories=0,status=0,menubar=0,scrollbars=0,copyhistory=0,resizable=0,width="+winwidth+",height="+winheight+",left="+left+",top="+top;
  var newwin    = window.open(winurl,winname,winopt);
}