Most people will not bother taking anything that you post. That said, do not post a whole story and always use a method where you can control access (use a link to your web page and not post it on someone elses). If you post a whole or even most of a story, it is considered published and many places will only publish first rights on a story. This means you can't sell it. The copyright issues are detailed in the copyright website at the Library of Congress. It is the best place to read up if you are worried about what can happen if you post.