function createXMLHTTP() 
            {
                        var ajax;
                        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.");
            }