[canip]

Why can i not post my server in the Server Advertisements.

It say:

canip, you do not have permission to access this page. This could be due to one of several reasons:

Your user account may not have sufficient privileges to access this page. Are you trying to edit someone else's post, access administrative features or some other privileged system?
If you are trying to post, the administrator may have disabled your account, or it may be awaiting activation.

[FaceTutorialz]

I think you have to had 5+ reputation at least one time.

[Scenario]

http://forum.sa-mp.com/announcement.php?f=22

Read the part about the Server Advertisements section, it clearly tells you what you need to post in the board!

[xSiiLenTx]

you can earn reputation by making your own mapping or helping people on the forums, that way they will be greatful and give you some rep, when you get 5 rep you can post a server advertisement