Invalid XHTML 1.0 Transitional + Fix

line 665

  // author
  if ($entry['author'] == 0) {
     $author = "<b>" . check_plain($entry['anonname']) . "</b>";
  } else {
     $author = "<b>" . theme('guestbook_user_picture', $entry['author']) ."</b>";
  }

The theme_guestbook_user_picture has div's in it. having "div" within "b" violates this standard. I suggest removing them, this will require some css instead! OR!

  if ($entry['author'] == 0) {
    $author = "<b>". check_plain($entry['anonname']) ."</b>";
  }
  else {
    $author = theme('guestbook_user_picture', $entry['author']);
  }

Line 641 needs to have b tags!

$output .= '<div class="submitted"><b>'. t("Visit !username's profile", array('!username' => $namelink)) .'</b></div>';

This is messy code, but it is the only way to get it to pass! I am not sure the "b" tag does anything for the non-anon user because I am doing an incredible amount of formating + some changes to the language (localization) module!.

I hope this helps