function getXmlHttpRequest()
{
   var xmlHttp = null;
   try { xmlHttp = new XMLHttpRequest(); }
   catch ( e ) {
      try { xmlHttp = new ActiveXObject( "Msxml2.XMLHTTP" ); }
      catch ( e2 ) { xmlHttp = new ActiveXObject( "Microsoft.XMLHTTP" ); }
   }
   return xmlHttp;
}