function update_counter(id){
	var xml_http_request_object = null;  
	if(window.XMLHttpRequest) // Firefox 
	   xml_http_request_object = new XMLHttpRequest(); 
	else if(window.ActiveXObject) // Internet Explorer 
	   xml_http_request_object = new ActiveXObject("Microsoft.XMLHTTP"); 
	else { // XMLHttpRequest non supporté par le navigateur 
	   alert("Votre navigateur ne supporte pas les objets XMLHTTPRequest..."); 
	   return; 
	} 
	var page = "php/counter/download_counter.php?id="+id;
	xml_http_request_object.open("GET",page, true); 
	xml_http_request_object.onreadystatechange = function() { 
	   if(xml_http_request_object.readyState == 4){ 
			var v = page; /*just to put an instruction*/
		}
	} 	 
	xml_http_request_object.send(null); 
}