Due to security concerns, newly registered users will have to make 2 posts before they gain full access to the site. This is just to make sure that new people are really interested in being here, and not just bots, spamming or other less-than-friendly activities.
On a related note, if your registration is rejected or deleted, it is probably because there is nothing in it that ties you to our topic here. Just write something in the registration information that shows you know what we talk about here. Also, gmail accounts with generic sounding names are the first thing that raise suspicion.