function criaXMLHttp() {
 if (typeof XMLHttpRequest != "undefined")
 	return new XMLHttpRequest();
 else if (window.ActiveXObject){
 	var versoes = ["MSXML2.XMLHttp.5.0",
 	"MSXML2.XMLHttp.4.0", "MSXML2.XMLHttp.3.0",
 	"MSXML2.XMLHttp", "Microsoft.XMLHttp"
 	];
 }
 for (var i = 0; i < versoes.length; i++){
 	try{
 		return new ActiveXObject(versoes[i]);
 	}catch (e) {}
 }
 throw new Error("Seu browser nao suporta AJAX");
}