Twitter is experimenting with sponsored text-ads on their website that show-up just after the “trends” section. The first round of text-ads mainly promoted Twitter apps and other services built around the Twitter ecosystem but that is no longer the case.
Twitter’s new ad format includes a website URL that takes you straight to the advertiser’s website (NFL in this case) and there’s a related hashtag to help you see related tweets on Twitter search.
A bit surprising thing about this new format is that nowhere does it says that these are advertisements or sponsored links. I could only figure that out after looking at the HTML source of the Twitter website (class = “promo”). Also they don’t use a nofollow for ads but that should not be an issue as the ads appear only in the timeline of logged-in Twitter users.