function openWindow( url, target, features ) {

  if( target == null ) target = "_blank";
  if( features == null ) features = "toolbar=yes,location=yes,menubar=yes,resizable=yes,scrollbars=yes";
  window.open( url, target, features ).focus();

  return false;
}

function openCustomWindow( url, target, width, height, features, centre ) {
  
  var f = "width="+width;
  if( centre ) f += ",left=" + ((screen.availWidth - width) / 2);
  f += ",height="+height;
  if( centre ) f += ", top=" + ((screen.availHeight - height) / 2);
  f += "," + (features != null ? features : "toolbar=no,menubar=no,location=no,resizable=yes,scrollbars=yes");

  window.open( url, target, f ).focus();

  return false;

}

function openCenteredWindow( url, target, width, height, features ) {

  return openCustomWindow( url, target, width, height, features, true ); 

}