var _POPUP_FEATURES = "\
  location=0,\
  menubar=0,\
  height=" + (screen.availHeight*80/100) + "px,\
  width=" + (screen.availHeight*80/100)*210/297 + "px,\
  left=" + (screen.availWidth - (screen.availHeight*80/100)*210/297)/2 + ",\
  top=" + (screen.availHeight - (screen.availHeight*80/100))/2 + "\
";



function raw_popup(url, target, features) {
  if ( typeof(features) == "undefined" ) {
    features = _POPUP_FEATURES;
  }
  if ( typeof(target) == "undefined" ) {
    target = '_blank';
  }
  var theWindow = window.open(url, target, features);
  theWindow.focus();
  return theWindow;
}



function link_popup(src, features) {
  return raw_popup(src.getAttribute('href'), src.getAttribute('target') || '_blank', features);
}