Does it show you the message it should show, or something like this:
Code:
<font color="red">Guests can not see images in the messages. Please register in the forum by clicking <a href="register.php"><strong>here</strong></a>.</font>]
Never mind, figure this out, the phrase should be entered in vBulletin language, not HTML. Here is what I entered and worked in 4.2.2:
PHP Code:
[COLOR=Red][SIZE=5]No Images for Guests.[/SIZE][/COLOR]