function fetch_query_tag( source, names )
{
  if( !source )
    return fetch_query_tag( location.search, ['tags'] ) ||
	   fetch_query_tag( document.referrer, ['tags', 'q'] );
  var peeker, i, tag;
  for( i=0; i<names.length; i++ )
  {
    peeker = new RegExp( '[?&]'+ names[i] +'=([^&]*)', 'i' );
    if( (tag = peeker.exec( source )) )
      return unescape( tag[1] );
  }
  return '';
}