Go to edit, and then see if the delete option is there. If not ,it is because after a certain amount of time, you are unable to delete your post.
after specific time period u can't delete post maybe if u will contact admin and tell him reason he will do it 4u
The solution : think twice before making a post. Choose the right words. Or if that meaningless, better not post anything. Just my opinion.
The safest way is pm any of the moderator and ask them that you want to delete..... But if the posts are too old now, then its better forget about it... dump it!!!