Twitter is now back up for most people. We're waiting on confirmation from the team at Twitter that the issue has been completely resolved. You can follow along at https://status.twitterstat.us/ for more information.
Twitter has identified the outage, which was due to an internal configuration change, which they're now fixing. Some people may be able to access Twitter again. Twitter is working to fix the problem for everybody as soon as possible.
Twitter is currently experiencing an outage, resulting in messages not being able to be sent/received. The team at Twitter is currently investigating and we are monitoring the issue on our end. You can follow along at https://status.twitterstat.us/ for more information.