Twitter rolls out new design for web
No edit button yet, Twitter's yet to decide if that's important or not.

More of What’s Happening: Twitter has brought over Explore to bring you the content found in the apps; expect more live video and local moments depending on your location. Get context with profile information within conversations and check out your Top Trends.
Easy Access to Your Favorite Features: Bookmarks, Lists, and your Profile are right up front and have their own spot on the side navigation, making it easier and faster to jump between different tabs.
Direct Messages All in One Place: Direct Messages have been expanded so you can see your conversations and send messages all from the same view. Now there’s less hassle switching between screens to send a message.
Login, Logout Struggle No More: Whether you have one profile or a few, now you’re also able to switch between accounts faster, directly from the side navigation.
Today is a big step as Twitter continues to be in relevance more than ever. Initial reactions to the redesign have generally been unfavorable and personally I'm not a fan either however, I guess that's familiarity breeding contempt and we're usually not well versed with change.
If you're not a fan of the redesgin there's always Tweetdeck and Tweeten.