function updatedisctrict(str)
	{
		var xmlhttp;
		if (window.XMLHttpRequest)
			{// code for IE7+, Firefox, Chrome, Opera, Safari
				xmlhttp=new XMLHttpRequest();
			}
		else
			{// code for IE6, IE5
				xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
			}
		xmlhttp.onreadystatechange=function()
		{
			if (xmlhttp.readyState==4 && xmlhttp.status==200)
			{
				document.getElementById("district_list").innerHTML=xmlhttp.responseText;
			}
		}
		xmlhttp.open("GET","update_district.php?cat="+str,true);
		xmlhttp.send();
	}