Guest Message

I was wondering if you can create a message on your Homepage Message that only guests can read:

E.g.

Code:

<script type="text/javascript">
if(pb_username == 'Guest')
document.write("You are not logged in")
</script>

Or you could at least tell me what cookie I should be looking for...

Is it:
fa_forumcloud_forumotion_com_t
or
fa_forumcloud_forumotion_com_sid

And what is the Guest/Username variable?

Ignored "bump".

before , i got a questions where should i put this ?
can u please explain it ! its a good idea this code but i dont realy know
where put it . thank u !