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 nao 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.");
}