Question

why does the gaudian sylph Ariel warn Belinda?

Answer 1

Here are several really good websites about Shakespeare and his works and his times:

http://shakespeare.palomar.edu/

http://www.shakespeare-online.com/

http://www.bardweb.net/

http://www.enotes.com/william-shakespeare/

http://nfs.sparknotes.com/
This may be the best of all. Find the play you're reading and then the Act and Scene you need. You'll then be able to read the original text on the left and a modernized text on the right.

http://www.sparknotes.com/shakespeare/