Some good cryptography modules are found in Digest-MD5 from CPAN. I like Digest::MD5, personally.

Of course, the encryption has to be undone to be displayed in a browser. Unless you're programming for a specific plugin which has the appropriate decryption keys or algorithms, people will be able to see your HTML anyway, at some point.

In my opinion, it's not worth the trouble as any security it will give you is more for show than effect.