If you really want to waste bandwidth and annoy your visitors when they want to do legitimate things with the right click function then google will find you some free scripts.
The menu available through a user's right mouse button is called the "context menu". It's content can change, depending on where the mouse is at any particular time (over text, an image, etc.). While it can be addressed and disabled or replaced with some Javascript, newer browsers have a configuration item that specifically looks for "context menu" manipulation code, and disallows it. As far as I know, Internet Explorer is the only browser that doesn't give the user the ability to disable "context menu" alteration. I use Firefox mostly and always have "context menu" manipulation disabled.
If you were going to mess with a visitors right click ability, a better approach would be to replicate the "context menu", in all it's forms, and only disable certain items. Then, a visitor might not notice that one or two items were removed, if all the other functionality still existed. But to implement something like that would require a lot of knowledge about Javascript and require more work than most users would want.
