Do not access the $_GET global variable directly.  It's a security risk.  At minimal sanitize the variables using http://us1.php.net/manual/en/function.filter-input.php.  Even better use http://us1.php.net/manual/en/function.filter-input.php.  This allows the parameters to be available in templates.  You can add your query vars here:  https://github.com/topcoderinc/tc-site/blob/dev/wp-content/themes/tcs-responsive/functions.php#L171