To a new arrival, Dixonary players seem like a band of scofflaws, applying the rules they like and ignoring the ones they don't, and generally making things up as they go along. But appearances can be deceptive, and the rules are in fact quite rigid. They just haven't been written down lately. The only official rules are the ones published on CompuServe in 1990.
This is hard on new players. The 'Real' Rules are for them, especially when they have to deal for the first time, and conscientiously read the 1990 Dixonary Rules, only to discover they have been playing a rather different game. Despite these rules' being unofficial, you will not get into trouble if you play as if they were official. That cannot be said for the 1990 rules: if you take those rules at literal face value you risk getting blasted for not knowing how the game is really played.
There is also a quick-start Basic Rules summary.