it's an arrow pointing up constucted from a forward and back slash, it usually indicates that there is something worth noticing above

( Lightguy hail satan, Mon 22 Jun 2009, 14:56, archived)

ITS A TEEPEE!

(likeajackhammer, Mon 22 Jun 2009, 14:57, archived)

doctor doctor, i'm a teepee, i'm a wigwam!
calm down, you're two tents.
( Lightguy hail satan, Mon 22 Jun 2009, 14:58, archived)

although not in this case

( manolith hooray for me, Mon 22 Jun 2009, 14:58, archived)