A web site that turns its nose up at legitimate, fully-functional browsers, such as IE 7 or Firefox simply because the webmaster won't tolerate his site being viewed using off-brand browsers and can't be bothered to update the site's script to recognize legitimate browsers.
Some monopolistic corporations, such as MyCrudSoft, are browser snobs. You have to do business with them on their terms because they don't even need to care whether you like doing business with them. It's their way making sure you know that they don't have to give a crap about you.
Can you define these popular missing words?