Did you finish all seven levels of this website? If you did, you should have a good knowledge of English grammar and usage. Do you believe you have accomplished something? If so, you deserve to receive a certificate. It looks like this:
click on the image
If you did not finish all seven levels (Blue, Red, Yellow, Green, Purple, Orange, Violet), you should not print out the certificate. But if you did--and you are on your honor here--you can print out this certificate and sign your name on the line.
Do you swear--honestly and in accordance with your conscience--that you finished all the lessons? Then go ahead and print out your certificate. Congratulations!