function GetXMLHttp(){
	var xmlHttp;
	try{
		xmlHttp = new XMLHttpRequest();
	}
	catch(ee){
		try{
			xmlHttp = new ActiveXObject("Msxml2.XMLHTTP");
		}catch(e){
			try{
				xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
			}catch(e){
				xmlHttp = false;
			} 
		}
	}
	return xmlHttp;
}
var xmlRequest = GetXMLHttp();

function cotacao(){
	xmlRequest.onreadystatechange = mostraCotacao;
	xmlRequest.open("GET",'Scripts/dolar.php',true);
	xmlRequest.send(null);
}

function mostraCotacao(){
	if(xmlRequest.readyState == 4 && xmlRequest.status == 200){
		document.getElementById('cotacoes').innerHTML=xmlRequest.responseText;
	}
}