You have to have over 20 posts for some privileges and over 50 for others. There is an explanation of all that somewhere. I'll see if I can find it and post the link .......
do have a read of this it's a big help - but here's the bit you were asking about ....
:sign0144:When you are a newbie
You are in a group which has no avatar, limited signature space, no Private messaging other members, no sending email to other members and you cannot upload images to the gallery.
When you reach 20 post s's you get avatar privileges and a larger signature space and can upload images to the gallery.
When you reach 50 posts, you get even more signature space, and private messaging and emailing is enabled.
I hope you understand the privileges that you will receive for being a long term poster.