Members can edit their posts for 30 minutes after the initial posting, but they cannot delete their posts.
To edit your posts, click the
button by the post you want to edit. After you have made your modifications, a note will appear, which notifies other users that you have edited your post. Administrators and moderators can also edit your messages.
The reason for the edit time window is that without it we used to have posts being made, then someone would add a reply, then the original poster would change their original post. This was fairly common in debates where someone would change what they originally said then claim they'd never said it :(