var request = false;
try {
 request = new XMLHttpRequest();
} catch (trymicrosoft) {
 try {
   request = new ActiveXObject("Msxml2.XMLHTTP");
 } catch (othermicrosoft) {
   try {
	 request = new ActiveXObject("Microsoft.XMLHTTP");
   } catch (failed) {
	 request = false;
   }  
 }
}

if (!request)
 alert("Error initializing XMLHttpRequest!");


//======
function selects_block(region_id) {
	var url = "/inc/a_select_city_block.php?region_id="+region_id;
	request.open("GET", url, true);
	request.onreadystatechange = update_select_block;
	request.send(null);
}
function update_select_block() {
	if (request.readyState == 4)
		if (request.status == 200){ 
			$("#selects_block").html(request.responseText);
		}else {
		alert(request);
			if (request.status == 404) 
				alert("Request URL does not exist");
			else alert("Error: status code is " + request.status);
			}
}
//=======


//======
function refreshFirms(cat_art) {
	var url = "/inc/refresh_firms_selects.php?cat_art="+cat_art;
	request.open("GET", url, true);
	request.onreadystatechange = update_firms;
	request.send(null);
}
function update_firms() {
	if (request.readyState == 4)
		if (request.status == 200){ $("#firms_block").html(request.responseText);
		}else
			if (request.status == 404) alert("Request URL does not exist");
			else alert("Error: status code is " + request.status);
}
//=======