If you ONLY want that line to not show up on the register or login page (like what if they go to forumdisplay.php? or showthread.php?), then you may want to try this instead:
HTML Code:
<if condition="$show['guest'] AND (THIS_SCRIPT != 'login' OR THIS_SCRIPT != 'register')">
<meta HTTP-EQUIV="REFRESH" content="0; url=www.mysite.com/website/blah">
</if>
That basically says If the user is not loggin in (they are a guest) AND they aren't on the login or register page, then......