Posts are moderated until your reputation reaches a certain level. I think its when you reach the fourth green square, but I'll find out for certain. Not all your posts are moderated before they are visible though. You can post right away in the General and off topic areas, as well as Newt and Salamander help and the whole Axolotl section. The ones that are moderated, like the advanced species topics and the Vivaria section are often turned to by occasional users and non members as being 100% factual and correct as far as we know at present, so its important to keep them free from anything that isn't.