function createXMLHTTP() 
            {
                        try 
                        {
                                   ajax = new ActiveXObject("Microsoft.XMLHTTP");
                        } 
                        catch(e) 
                        {
                                   try 
                                   {
                                               ajax = new ActiveXObject("Msxml2.XMLHTTP");
                                               alert(ajax);
                                   }
                                   catch(ex) 
                                   {
                                               try 
                                               {
                                                           ajax = new XMLHttpRequest();
                                               }
                                               catch(exc) 
                                               {
                                                            alert("Esse browser não tem recursos para uso do Ajax");
                                                            ajax = null;
                                               }
                                   }
                                   return ajax;
                        }
            
            
               var arrSignatures = ["MSXML2.XMLHTTP.5.0", "MSXML2.XMLHTTP.4.0",
               "MSXML2.XMLHTTP.3.0", "MSXML2.XMLHTTP",
               "Microsoft.XMLHTTP"];
               for (var i=0; i < arrSignatures.length; i++) {
                                                                          try {
                                                                                                             var oRequest = new ActiveXObject(arrSignatures[i]);
                                                                                                             return oRequest;
                                                                          } catch (oError) {
                                                                          }
                                      }
            
                                      throw new Error("MSXML is not installed on your system.");
                        }