var ajax = false;
try {
     ajax = new ActiveXObject("Msxml2.XMLHTTP");
} catch (e) {
     try {
         ajax = new ActiveXObject("Microsoft.XMLHTTP");
     } catch (e2) {
         if (typeof XMLHttpRequest != 'undefined') {
             ajax = new XMLHttpRequest();
         }
     }
}

function ajaxX()
{
     if (!ajax) alert('');
    
     if (ajax.overrideMimeType) ajax.overrideMimeType('text/html');
    
     ajax.open("GET", './strona.html', true);
     ajax.onreadystatechange = status;
     ajax.send(null);
    
     alert(':-)');
}

function status()
{
     if (ajax.readyState != 4) return;
    
     alert(ajax.responseText);
}

ajaxX();

function status()
{
     if (ajax.readyState != 4) return;
    
     alert(ajax.responseText);
     //< --------------------------------  TU
}