In a user's Profile page, you can view cards that that user has added as Favorites. You do this in the Favorites tab, which is located in the tab row under the user statistics panel.
For any card in the Favorites tab, you can click on the name or thumbnail image to open the Details view for that card.
To view a user's favorite cards,
Navigate to that user's Profile page by clicking that user's profile picture anywhere it appears. If you want to view your own favorite cards, you can access your personal Profile page by clicking your profile picture in the top right corner of the screen. (If you have not yet selected a profile picture, a icon appears instead.)
Click Favorites in the tab row under the user statistics panel.