function Querystring(qs) {
	this.params = {};

	if (qs == null) qs = location.search.substring(1, location.search.length);
	if (qs.length == 0) return;

		qs = qs.replace(/\+/g, ' ');
		var args = qs.split('&'); // parse out name/value pairs separated via &

		for (var i = 0; i < args.length; i++) {
			var pair = args[i].split('=');
			var name = decodeURIComponent(pair[0]);

			var value = (pair.length==2)
			? decodeURIComponent(pair[1])
			: name;

			this.params[name] = value;
		}
	}

	Querystring.prototype.get = function(key, default_) {
		var value = this.params[key];
		return (value != null) ? value : default_;
	}

	Querystring.prototype.contains = function(key) {
		var value = this.params[key];
		return (value != null);
	}