To verify if you have an account on this website, use the Recover Password option and enter your most used emails. If you'll receive a recovery email then that's the confirmation you've registered on the website. It's a simple trick to find out what email you've used to register in the past or not. If you actually don't have an account, visit the main page and click on the Register button located on the upper-right section of the website. Fill in the forms with real data and you'll then receive a confirmation email. Confirm your account then you will have the possibility to use the website's features (ask questions, manage your questions, bookmark interesting questions,etc).