Nothing ticks me off more than people who put these "Right Button Disabled" things on their websites. I use the right button to navigate sights (e.g. Back | Forward | etc.) almost exclusively.
I don't care how good a site is (or thinks it is) -- if I click the right button and get a "Menu Disabled!" pop-up, I'm never coming back. It's utterly pointless, and just limits the user's functionality. Anybody who really wants to look at the site's code can still do it in a variety of ways.
It really is very, very poor design to disable the right-button.