var objAjax;

        function getHTTPObject(){
                if(window.XMLHttpRequest){
                        return new XMLHttpRequest();
                } else
                if(window.ActiveXObject){
                        var prefixes = ["MSXML2", "Microsoft", "MSXML", "MSXML3"];
                        
                        for(var i = 0; i < prefixes.length; i++){
                                try{
                                    return new ActiveXObject(prefixes[i] + ".XMLHTTP");
                                } catch (e) {}
                        }
                }
        }


        function executaRemoto( fRetorno, sMetodo, sURL, sParametros ){
                objAjax = getHTTPObject();
                objAjax.onreadystatechange = fRetorno;
                objAjax.open(sMetodo, sURL + "?" + sParametros, true);
                objAjax.send(null);
        }


        /* exemplo de funcao de retorno
        function retornoAtivacao(){
                if (objAjax.readyState == 4){
                        if( objAjax.responseText == "true" ){
                                selecaoAnterior = "img/estrela-amarela.gif";
                        }
                        else{
                                selecaoAnterior = "img/estrela-cinza.gif";
                        }
                }
        }
        */