Gnupg – is it a good idea? – Firefox / Chrome in encrypted content

I am currently thinking about writing a Firefox / Chrome plugin and also Python / PHP / JS to achieve the following:

Assuming you are in a secure non-SSL site or simply do not trust any CA as it allows Encrypt, Comodo, Symantec, etc. But you still want to achieve the maximum. Security for your customers / users. What happens if you give each user the ability to enter their PGP public key in the configuration of their account or registry and then encrypt all the html content that they send to the client with their public key? After receiving the message pgp-message or "pgp wrap html message", the Chrome / Firefox add-on decrypts the received pgp message and shows it as html as a normal website. For this concept, you do not need any CA or SSL because the correct decryption can only be done if the plugin contains your Privat-Key file to decrypt the received content.

From what I understand of SSL, only the connection is encrypted but not the actual content. Tell me what you think? Do I miss something here or is it just a good idea?