While you are building up your posts to that golden number of 15, there are some things that you can’t do that the system will spot. These things will result in an error message and your content will not be posted. The reason that we enforce this spam filter for your first 15 posts, is because we get inundated with people registering bot accounts and posting spam URLs, so we're doing our best to weed these accounts out. This spam prevention system is triggered by several things, including links, and words or phrases that are often used by spammers. For example, things like domain names, spammed sites or phrases like "skype" or "contact me". Once you've made 15 good quality posts, your content will not be subject to the spam management filter. So while you are really new, keep your posts introductory, without any links, and you should be fine.