Only mods can delete a post or a thread. You can edit a post within a certain amount of time, the amount of time varies between boards. For most of them, the edit time is 30 minutes. If you can edit a post, the button will be in the left corner of the post beside your name, the time you posted and the report button.
Further to what Mavjade said, if you have posted something in error - like a thread in the wrong forum or a double post - you can use the report function to alert us and ask that the error be fixed. All of the mods can see the reports. Just click on 'report' at the bottom of your post.
