Twitter created a mobile version of the Twitter web site.

Technically speaking, Twitter has always been mobile because you can send and receive messages over SMS. However, there's more and more folks accessing the mobile web from smart phones these days and then Twitter's guys created a mobile version of the web site.

So if you have a browser-enabled phone, head over to m.twitter.com and catch up with your friends, mobile style.

Twitter has also introduced a new feature lots of folks requested called "block." Blocking someone means that you (and your pic) will not appear on the blocked person's friends list, profile page, friends timeline, badge, or anywhere else. The person will not be notified that they've been blocked, but they will be unable to add you as friend. The feature is a hyperlink in the sidebar of Twitter profile pages.