Thanks Chuck, I did notice the arrows on the right but I didn't know they were new post icons. It would be great if they were on the left so that they follow the forums look and theme. I think most of my users, like me, didn't look at the arrows on the right or don't know what they're for.
Just one more thing, I posted a few test replies from a test user on another computer, and then when I browsed the classified page the icons on the right remained as 'nonewposts.gif'. I presume these should change if someone has replied to an advert, or does it only change when someone posts a new advert?
Thanks so much for your help.