To reproduce:
Go to Card Database MTG (or other db)
Select a card in the list (Checking the checkbox)
Click the Cards Action button
In the dropdown my decks are listed
When i hover over one of my decks there is another fold out happening, but its only a black line.
I would expect either a button sayin add or something to be shown there, or nothing at all. It should be sufficient to click my deck name to add the card/cards.
Anyway, there is no way of adding cards to a deck. And if there is another way of adding cards to a deck, it's not at all apperent to the user.
To me this seams to be a MAJOR bug. This function was one of the major ones for me to even join the site.
I have tried this on a Windows 8 machine in
Chrome Version 32.0.1700.107 m,
Firefox 23.0.1
Internet Explorer 1.0.9...
Same bad result every time.