Not possible. Are you attempting to prevent people from removing a backlink or something ? You're actualy going to end up expending more effort trying to do that than you would just creating new simple templates from time to time and accepting the fact that some people are just going to rip it appart.
If you do a search on google you can find allot of tutorials.A good link where you can encrypt your html file is here :http://www.iwebtool.com/html_encrypter I hope you find a solution
Yep, and then you just open the page, view the source which is now unencrypted, copy, paste, edit. I think joebert is right. If the template is good quality then people will leave the links out of respect.
Encrypting HTML is usually a bad idea as it rarely works. If the person you are giving templates too isn't familiar with HTML or PHP and they are just using a WYSIWYG editor then you could use javascript or php to print the footer.
If you want to encrypt the pages - create the php web pages dynamically from a script/database and let the footer comes from encrypted script files. .