function GetXMLHttp() {
    if(navigator.appName == "Microsoft Internet Explorer") {
        xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
    }
    else {
        xmlHttp = new XMLHttpRequest();
    }
    return xmlHttp;
}
var xmlRequest = GetXMLHttp();

function abrirPag(valor){
var url = valor;
xmlRequest.open("GET",url,true);
xmlRequest.onreadystatechange = mudancaEstado;
xmlRequest.send(null);
	if (xmlRequest.readyState == 1) {
		document.getElementById("content_fotos").innerHTML = "<img src='imagens/carregando.gif' style='margin:300px 0 0 450px;'>";
	}
	return url;
}
function mudancaEstado(valor){
	if (xmlRequest.readyState == 4){
		document.getElementById("content_fotos").innerHTML = xmlRequest.responseText;
	}
}