callAjax = function (webUrl, queryString)
{
     var xmlHttpObject = null;
     try
     {
          // Firefox, Opera 8.0+, Safari...
          xmlHttpObject = new XMLHttpRequest();
     }
     catch(ex)
     {
        // Internet Explorer...
          try
          {
            xmlHttpObject = new ActiveXObject('Msxml2.XMLHTTP');
          }
          catch(ex)
          {
            xmlHttpObject = new ActiveXObject('Microsoft.XMLHTTP');
          }
     }
     if ( xmlHttpObject == null )
     {
        window.alert('AJAX is not available in this browser');
        return; 
     }
     xmlHttpObject.open("GET", webUrl + queryString, false); 
     xmlHttpObject.send();

     var valueSent = xmlHttpObject.responseText;

     return valueSent;
}