function GetXMLHttp() {  
    if (navigator.appName == "Microsoft Internet Explorer") {  
        xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");  
    } else {  
        xmlHttp = new XMLHttpRequest();  
    }  
    return xmlHttp;  
}  
var mod = GetXMLHttp();  
  
function comboCidades(valor) {  
    mod.open("GET", "combo-cidades.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);  
}