In my personal opinion, you shouldn't diable right click menus. They have multiple purposes -- to translate pages, to move back and forward, to print, to change chararacter encoding and more.

By disabling that, you limit the user. If they have special needs, you potentially interfere with the browsing of your website.

Also I don't know what the purpose of disabling it is (maybe trying to stop people viewing the source or taking an image) but people can do that anyway, if they want to. So all you do is delay someone who wants to take something by about 2 seconds, whilst upsetting your visitors.

But as I said, just my opinion as a web designer and internet user.

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I'd start a revolution, if I could get up in the morning.