If you make a lot of purchases from the Mac App Store, your Purchased tab can get very unwieldy. Fortunately it's easy to fix.
The Purchased tab in the Mac App Store shows you all the apps you've downloaded, including those from Apple like Keynote, Pages, Numbers, GarageBand and iMovie. Free apps and paid apps alike appear there ? literally everything you've downloaded from the Mac App Store. This tip helps you tame that Purchased list so you only see what's still relevant to you.
Full story from the iMore Blog...