// Return tag link
// Argument: 'css' or array( 'css' ) or array( 'css', 'design' )
function ozh_get_tag_link( $tags = array() ) {
    if( !$tags )
        return get_home_url();

    global $wp_rewrite;
    $tags = implode( (array)$tags, '+' );

    if( $perm = $wp_rewrite->get_extra_permastruct('post_tag') ) {
        // we have pretty permalinks
        return trailingslashit( get_home_url() ) . str_replace( '%post_tag%', $tags, $perm );
    } else {
        // default links eg http://bleh.com/?tag=bleh
        return trailingslashit( get_home_url() ) . '?tag=' . $tags;
    }
}