function getParameter (parameterName) {
      queryString = window.top.location.search.substring(1)
      // Add "=" to the parameter name (i.e. parameterName=value)
      var parameterName = parameterName + "=";
      if ( queryString.length > 0 ) {
        // Find the beginning of the string
        begin = queryString.indexOf ( parameterName );
        // If the parameter name is not found, skip it, otherwise return the value
        if ( begin != -1 ) {
          // Add the length (integer) to the beginning
          begin += parameterName.length;
          // Multiple parameters are separated by the "&" sign
          end = queryString.indexOf ( "&" , begin );
          if ( end == -1 ) { end = queryString.length }
          // Return the string
          return unescape ( queryString.substring ( begin, end ) );
        }
        // Return "null" if no parameter has been found
        return "";
      }
    }