You dont have to actively download anything. Any picture that you see online has already been "downloaded" to your machine. So if the front page of that site has any illegal images, I cannot see a way that one would be completely safe since you are actually in possession of those images. I doubt you would be prosecuted, but it's best to play it safe.
Look at it this way. If you find a bag of crack on a street corner, pick it up, and turn it into the police, you *could* be hit for possession since you, well, had it in your possession. This is one reason why im not a huge fan of laws that make it illegal to simply touch an object or piece of data.