/**
 * Cria um objeto XMLHttp, suporte a IE sux.
 * @return objeto XMLHttp
 */
function criaXMLHttp() {
	if (typeof XMLHttpRequest != "undefined") 
		return new XMLHttpRequest();
	else if (typeof ActiveXObject != "undefined") { // suporte ao IE 7
		var aVersoes = ["MSXML2.XMLHttp.6.0", "MSXML2.XMLHttp.5.0",
		"MSXML2.XMLHttp.4.0", "MSXML2.XMLHttp.3.0",
		"MSXML2.XMLHttp", "Microsoft.XMLHttp"
		];
		for (var i = 0; i < aVersoes.length; i++){
			try{
				return new ActiveXObject(aVersoes[i]);
			}catch (e) {}
		}
	}
	// se nenhum objeto xmlhttp for suportado
	throw new Error("Seu browser nao suporta AJAX");
}