Hai.
I was using Facebook social networking, but I forget my email address through which I have registered.
Tell me how to find the email address through which I have opened a Facebook account?

If you've made your info public you can see it on your info page, provided you can find your Facebook profile.

You should have received a confirmation email to that address. Maybe check your deleted folder.

You can always make a new page.

Did you sign on using Firefox?