From my tests you can also start a new test on your card sets and custom card sets. To start a new test on somebody else's card set you need to find it elsewhere in the site. From my test you can also delete one or all of your old tests. If you don't care to keep a history of your test results please delete them. Any number of card sets and custom card sets can be downloaded.
Wireless cards displays a list of which sets have been flagged to be downloaded.
Card sets can be added to this list when reviewing or testing yourself on a card set, or from any card set list. Custom sets can be added to this list from custom sets . In the wireless cards area you can remove card sets you no longer wish to download from the list. Registerd users can take a graded test on any card set, custom card set or on your marked cards. If you don't want a grade or don't want to register you can still test yourself on flashcards through the review page.