With one of the most popular apps out there, Youtube wanted their users and visitors to get the same experience when they visit the desktop site and so they unveiled a new cleaner responsive website.
From Youtube's blog:
YouTube now has a center-aligned look, fitting neatly on any screen size, and feeling similar to the mobile apps you’re spending almost half your YouTube time with. You can quickly flip between what’s recommended and popular in “What to Watch” like Postmodern Jukebox’s Timber, and the latest from your subscribed channels like iamOTHER in “My Subscriptions,” with both options now front and center. Click the guide icon to the right of the YouTube logo at any time to see your playlists, subscriptions and more.source››youtube blog
