Google has continued to improve Hangouts since it was released to fully replace Google Talk as the main messaging solution for its users. We recently saw Google reintroduce the ability to see which of your friends are online, and now the company has included a new tab on the GMail version of Hangouts, which puts online contacts on top.
Its still possible to message your offline friends, but you will have to scroll down to find them on the list. Many of us have contacts we want to keep at the top of the list regardless of their online status (a significant other, a good friend, maybe even a parent), so Google has also added the ability to pin people them there. Just right-click and select the option.
The feature may take awhile to appear for all users, as it is still rolling out. If you see the new online user sorting on your contacts, leave us a comment and let us know.
source - Google