They do this with some basic javascript, but this does not actually hide your HTML source! In many browsers you can simply go to view->source on the menu. Even if you couldn't, it is trivial to simply load up a debugging proxy like Fiddler, or packet-sniff the connection.

It is impossible to effectively hide the HTML, JavaScript, or any other resource sent to the client. Impossible, and isn't all that useful either.

Furthermore, don't try to disable right-click, as there are many other items on that menu (such as print!) that people use regularly.