function montaXMLHTTP(){
try{
    myObj = new XMLHttpRequest();
}catch(ee){
    try{
        myObj = new ActiveXObject("Msxml2.XMLHTTP");
    }catch(e){
        try{
            myObj = new ActiveXObject("Microsoft.XMLHTTP");
        }catch(E){
            myObj = false;
        }
    }	
}
return myObj;
}
 
 obj_mostra = new montaXMLHTTP();
 
function ler(){
    conteudo = '';
	var anofoto = document.getElementById("anofoto").value;
	conteudo = "<div style='color:#FF0000; font-size:14px; padding:30px;'>Carregando...</div>";
	document.getElementById("principal").innerHTML = conteudo;
    obj_mostra.open("GET","principal.asp?anofoto="+anofoto,true);
	obj_mostra.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
	obj_mostra.onreadystatechange = function(){
		if(obj_mostra.readyState == 4){					
                conteudo = obj_mostra.responseText;
				document.getElementById("principal").innerHTML = conteudo;
							
		}
	}
	obj_mostra.send(null);
}