В че тут ошибка?
echo '<div class="head"><table style="width: 100%;"><tr>' .
'<td valign="bottom"><a href="' . $set['homeurl'] . '"><img src="' . $set['homeurl'] . '/theme/' . $userskin . '/images/logo.png" alt=""/></a></td><td align="right">' .
($user_id ? 'Вы:<a class="link" href="' . $set['homeurl'] . '/users/profile.php?act=office"><span class="red">' . mb_substr($login, 0, 1) . '</span>' . mb_substr($login, 1) . ' </a>' : '') .
($user_id ? '' : '<a class="link" href="' . $set['homeurl'] . '/login.php">' . $lng['login'] . '</a> <a class="link" href="' . $set['homeurl'] . '/registration.php">' . $lng['registration'] . '</a>' : '') .
'</td></tr></table></div>';