All 78 cards, one a day. Five up front, so there's something to start from.
A collection is built over weeks, and a browser is no place to keep one - clear your cache and it's gone. Register and you get five cards straight away, then one a day. There are 78 in the deck.
Your deck is whichever of the seventy-eight you already hold. You do not need it to read meanings: all 78 cards are written up and open to everybody. You need it for the table - a reading is drawn only from what you have collected, which is why it gets fuller and more interesting over time.
Five arrive at once when you register. After that, one a day for the free reading: the day's card stays with you. The order is random, so the majors come mixed in with the minors rather than at the end. Collecting all seventy-eight is a few months' work, and that is the normal pace.
Because a deck you assembled reads differently. A card that came to you on a particular day is remembered along with that day - and when it turns up in a reading it already has your own context attached, not only a dictionary entry. That is the whole reason; no card can be bought for money.