function getHTML(url,divResult) {
    
    new Ajax.Request(url, {
        method: "get",
        requestHeaders: ['If-Modified-Since', new Date(0)],
        onLoading: function(transport){
             
            
        },
        onSuccess: function(transport) {
            
            var valueHTML = transport.responseText;
            
            
            if(divResult!="" && document.getElementById(divResult)!=null)
               document.getElementById(divResult).innerHTML=valueHTML;
            else if(document.getElementById(divResult)==null)
               alert("No existe contenedor: "+divResult);  
            
          
        }, 
        onFailure: function(transport) {
            alert(transport.responseText);
        }
    });
    
    return false;
}

function cargarMenu()
{
   getHTML("menu.php","lista1");
}