If you decide to delete your facebook account permanently then this tutorial is for you. In facebook when you deactivate your account from Account page, your profile and all information associated with it are inaccessible to the other users.
In future if you decide to use your account ,you can just log in and retrieve the facebook page by selecting activate option.
If you want to delete permanently means then log in to your account and visit this link
When you click this page it will display the form to fill and ask whether you want to delete permanently
Fill the form and click ok.