New posts since last visit

There already is the exact same function by default.
You sure you're logged in and not a guest?

i am logged in

Create a test user, logg on as the test user. Post i a forum, logg out and then logg in as yourself. You should see the change in icon next to the forum. Make sure your theme really has a different icon that is shown on new posts.

And of course, you won't see a yellow envelope if you are the one who typed the new post ;)

Wait a minute,do you need to logout then login on next visit to be able to see new posts,so if you are constantly logged in even though you switch you computer off you will not see new posts.

No, you don't. We're just advising you to do it just so we know that you've tried everything and there isn't a silly mistake.
Give me the link to your PHPFusion site and I'll check it out?

Its ok,i got everyone to post and you could see there were new posts.I was going on the say so of another member but everything is now working,thanks for the replys.