Maybe they're just presenting the web site in a different way than intended by the maker. In how far is one obliged to follow the HTML standard when displaying a page? To run all the javascript? Get all third-party bits and pieces (e.g. advertisements)? Many Firefox add-ons change how a page looks like, by adding things, or blocking things. AdBlockPlus is a thorn in the eye of many advertisers, yet it seems they can't do much against it.
Call my argumentation ridiculous - I know it is. But it is that kind of interpretation is what opens up mazes in the law, and if you have your argumentation right, you may very well be within your legal rights.