There's many styles of "juiced" decks. Some are juiced by the seller, pre-marked. Some are juiced by the buyer, using vials of the dyes - different dyes for different colors on the card backs. Some use "daubs" - it's like juicing, but it allows you to mark a deck on the fly; as you receive a high card, you take some daub onto your fingertip and rub it onto the back of the card at a certain place, where it quickly dries and leaves a mark that you can detect. Some very sophisticated daubs and juices are invisible except in the ultraviolet spectrum - and the player using such marks wears a special pair of sunglasses (VERY expensive) to read the UV marks. There's also special daubs/juices for plastic cards, since many players and casino use plastic decks at poker tables.
Casinos are wise to these gamblers' devices - the "eye in the sky" and other cameras are able to filter light to try and spot these marks. The lower the tech you use, the less likely a casino will spot your marks on camera, but the more likely they'll spot them on the floor. It's also one of the reasons that casinos use deeper reds for their hearts and diamonds - the lighter reds don't show up as well on the cameras, particularly in the days when black-and-white cameras were the norm. While they're barred from communicating any information about your hand to the dealer or other players, they will compile information on your playing style to look for particular patterns that would indicate you're a cheater. They will end up barring you from the house, and you'll be blacklisted at all of the other casinos in the area, possibly even nationally - they share this information to protect each other and shut out cheats early and often in an effort to discourage them from attempting to come back.
The guy at markedcards.org works more specifically with gamblers than with magicians. His services aren't cheap, and most of the other items on his website are there for show - anything not related to gambling is generally out of stock, even if the website says otherwise. I know, I tried ordering from him before. I think in the near future he's planning to beef up the legit offerings he has to better hide the entirely-less-than-legit ones. Marked cards aren't illegal to create or possess in most places, but we all know how people feel about playing against someone using them against you! Using them in a money game would be construed as fraud, even if the game itself was illegal.
You won't find pictures of the card marks on his site for two reasons: many of the marking systems used won't show up well in a basic still camera, and he wants to keep his marking methods a secret so as to not inform the world of what to look for when a player is using one of his decks.
