I've been a professional Web designer for the last 9 years. I write html code every day. HTML stands for "HyperText Markup Language ." That's language as in French, English, German, etc. Anything you create and put on a public Web site is protected by copyright. You don't even have to put the copyright line at the bottom of the page, but it's better if you do.

Like a novel written in any language, the specific content which you or a contractor/employee you hire can be copyrighted. But you can't copyright a LANGUAGE. HTML is a LANGUAGE. I can write a novel in English and get it copyrighted. You can write a novel in English and get it copyrighted. Our works are both unique, but they're written in the same language. We don't get copyrights on the English language, we get them on the specific, unique works we've created using the language.

Likewise, specific, unique works you create in html (including images, Flash movies, etc.) are protected by copyright so you can sue somebody who plagarizes them. But trying to "protect" your source code is like trying to tell someone they can't write a book in English because you already have. Please, stop wasting time and effort on this futile pursuit.