So how you loop through querystring?

The QueryString property is a NameValueCollection object. So you can do something like this(example shown using C#):

foreach (string key in Request.QueryString.Keys)
{
    Response.Write(key+ " "+Request.QueryString[key]+"<br/>");
}

Request.QueryString[key] will give you the value for the key.

So if this is the url http://www.webcosmo.com/listing/Search.aspx?countryId=1&gId=2&dId=48

This loop with print out:

countryId 1

gId 2

dId 48