function getModels(f)
{
	
	var l1    = f.elements["marque"];
	var l2    = f.elements["model"];
	var index = l1.selectedIndex;
	if(index < 1)
	   l2.options.length = 0;
	else {
	   var xhr_object = null;
		
	   if(window.XMLHttpRequest) // Firefox
		  xhr_object = new XMLHttpRequest();
	   else if(window.ActiveXObject) // Internet Explorer
		  xhr_object = new ActiveXObject("Microsoft.XMLHTTP");
	   else { // XMLHttpRequest non supporté par le navigateur
		  alert("Votre navigateur ne supporte pas les objets XMLHTTPRequest...");
		  return;
	   }

	   xhr_object.open("POST", "getModels.php", true);
		
	   xhr_object.onreadystatechange = function() {
		  if(xhr_object.readyState == 4)
			eval(xhr_object.responseText);
	   }

	   xhr_object.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
	   var data = "marque="+escape(l1.options[index].value)+"&form="+f.name+"&select=model";
	   
	   xhr_object.send(data);
	}
}