function getAjaxRequest(get_which, req_id) {
 
    var serv_reply;
    try {
        // IE7, Firefox, Opera 8.0+, Safari
    	serv_reply = new XMLHttpRequest();
    }
    catch (e) {
        // Internet Explorer
        try {
        	serv_reply = new ActiveXObject("Msxml2.XMLHTTP");
        }
        catch (e) {
            try {
            	serv_reply = new ActiveXObject("Microsoft.XMLHTTP");
            }
            catch (e) {
                alert("Your browser does not support AJAX!");
                return false;
            }
        }
    }
    serv_reply.onreadystatechange = function() {
    	var container;
    	if (serv_reply.readyState == 4) {
    		var header = serv_reply.getResponseHeader("sent_which");
    		var newdiv = document.createElement("div");
    		newdiv.innerHTML = serv_reply.responseText;
    		switch (header) {
    			case "subcat":
    				document.getElementById('itemview').style.display = 'none';
    				container = document.getElementById("submenubox");
    				while (container.childNodes[0]) {
    					container.removeChild(container.childNodes[0]);
    				}
    				container.appendChild(newdiv);
    				container.style.display = "block";
    				break;
    			case "docview":
    				document.getElementById('itemview').style.display = 'none';
    				container = document.getElementById("itemview");
    				while (container.childNodes[0]) {
    					container.removeChild(container.childNodes[0]);
    				}
    				container.appendChild(newdiv);
    				container.style.display = "block";
    				break;
    			case "bio-works":
    				container = document.getElementById("itemview-data");
    				while (container.childNodes[0]) {
    					container.removeChild(container.childNodes[0]);
    				}
    				container.appendChild(newdiv);
    				container.style.display = "block";
    				break;
    			default:
    				alert("Σφάλμα AJAX: μη αναγνωρίσιμη απόκριση");
    				break;
    		}
    	}
    }

    var sUrl;
    /*	1=subcat
	 *	2=docview
	 *	-----------
	 *	3=bio
	 *	5=all_works
    */
    switch (get_which) {
    	case 1:
    		sUrl = "process_ajax_subcat.aspx?cat_id=" + req_id;
    		break;
    	case 2:
    		sUrl = "process_ajax_docview.aspx?subcat_id=" + req_id;
    		break;
    	case 3:
    		sUrl = "process_ajax_bio.aspx?des_id=" + req_id;
    		break;
    	case 5:
    		sUrl = "process_ajax_works.aspx?des_id=" + req_id;
    		break;
    	default:
    		alert("Σφάλμα AJAX: μη αναγνωρίσιμο ερώτημα");
    		break; 
    }
    serv_reply.open("GET", sUrl + "&rnd=" + Math.random(), true);
    serv_reply.send(null);
}