Dot Co was having some problems yesterday it was affecting some Twitter links.
The Next Web reported on the issue with the .co extension which now seems to have gotten fixed. If you are still having a problem, they posted Update: Some are reporting that .co domains are beginning to work again. Flushing your DNS cache may fix the problem. Here’s how on Mac or PC.
From the article:
Noticed that none of the links on Twitter are working today? It’s not just you! It looks like there’s a very serious problem with the .co top-level domain today, causing the t.co URL shorter to break.
Twitter shortens all links on its service using the t.co URL, which is affected by a problem on the .co domain that seems to affect a select number of people. For those affected, they’re unable to load anything on Twitter since all links require that domain.