Sep 2View Source
Here's what Wikipedia says about it:
Yahoo! Groups remodel 2013 "neo"
"On August 7, 2013, Yahoo! Groups rolled out another web-interface redesign, unannounced, to randomly chosen users, with no possibility of opt-out, even after complaints to Customer Care. Despite protests by Yahoo! Groups users (group owners, moderators, members) on the official Feedback Forum about unusability and multiple lost features "neo" continues to be rolled out."
Some of those lost features:
We cannot change what Yahoogroups calls our "cover photo"; you can no longer copy and save or even send our album photos out; we've lost our distinctive Homepage (the copy remains, but it's small); the copy and descriptions under each photo are gone. And more nasty surprises. Yahoogroups isn't the only venue out there, though, and many of the other forums are looking at making a change.