function get_parameter_on_query_string (parameterName)
{
	var queryString = "";
	var err;
	var value_parameter;

	try {
		queryString = window.top.location.search;
	} catch (err) {
		queryString = document.location.search;
	}

	var parameterName = parameterName + "=";

	if (queryString.length > 0) {
		begin = queryString.indexOf (parameterName);
		if (begin != -1) {
			begin += parameterName.length;
			end = queryString.indexOf ("&", begin);
			if (end == -1) {
				end = queryString.length;
			}
			value_parameter = unescape (queryString.substring (begin, end));
		} else {
			value_parameter = 'null';
		}
	}

	return value_parameter;
}