Default Avatar (if the user doesnt have one yet)

[Shinobi]

Hi, just a quick question....

I always see this on forums, you know when you first register, you havent uploaded an avatar yet, and if you look on their home page, where ur avatar is displayed, it has a "default" avatar, and it usually says something like, "No Avatar Used" i was wondering how to do that?? Ive got the avatar i want for the default, but how do i go about making it display for members who dont have an avatar yet??

Thanks