New New Twitter
You need to “navigate” your twitter feed to use the actions. So to “reply” to a tweet, scroll down using J and K (and space). You can see which tweet is highlighted. Then you can do an “action” such as hitting T to retweet.
For the “Timelines” you need to hold down G and hit the 2nd key, so to go to your profile, hold G and hit P.
Web developer should be thinking more and more of these keyboard shortcuts as your websites become more like applications.
Here’s a short of the help menu (you can hit “Shift+/” or “Shift + ?” to get this in twitter):