function GetXMLHttp() {  
if (navigator.appName == "Microsoft Internet Explorer") {  
xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");  
} else {  
 xmlHttp = new XMLHttpRequest();  
 }  
 return xmlHttp;  
 }  
var mod = GetXMLHttp();  
   
function alimentarCombo(valor) {  
mod.open("GET", "Carrega_ajax.asp?id="+valor+"", true);  
 mod.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");  
   mod.onreadystatechange = function() {  
        if (mod.readyState == 4) {  
             document.getElementById("resultado").innerHTML = mod.responseText;  
       }  
    };  
    mod.send(null);  
}