var http_request = false;

function makeRequest(url) {
   http_request = false;

   if (window.XMLHttpRequest) { // Mozilla, Safari,...
       http_request = new XMLHttpRequest();
       if (http_request.overrideMimeType) {
           http_request.overrideMimeType('text/xml');
       }
   } else if (window.ActiveXObject) { // IE
       try {
           http_request = new ActiveXObject("Msxml2.XMLHTTP");
       } catch (e) {
           try {
               http_request = new ActiveXObject("Microsoft.XMLHTTP");
           } catch (e) {}
       }
   }

   if (!http_request) {
       alert('Error: Nie można stworzyć instancji obiektu XMLHttpRequest');
       return false;
   }
   http_request.onreadystatechange = Contents;
   http_request.open('GET', url, true);
   http_request.send(null);
}

function Contents() {
   if (http_request.readyState == 4) {
       if (http_request.status == 200) {
          document.write(http_request.responseText);  
       } else {
           alert('Wystąpił problem z zapytaniem.');
       }
   }
}

<span name="ajax" style="cursor: pointer;" onclick="makeRequest('index.php?page=k')">Odpytaj</span>

document.write(http_request.responseText);

document.getElementById('div1').innerHTML = http_request.responseText;