If users were allowed to delete their own posts, then it causes great confusion to other members as well as a great number of broken links. Also, if you delete the first post in a long thread - then it will take the whole thread with it, which might not be fair on some other users. As Kitara suggests, if you have reason to delete a post please contact a moderator, their details can be found at the bottom of the home page - click "Forum Leaders".
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