If you've ever had a grey box pop-up in the middle of a YouTube video to correct spelling, add in some extra information or link you out to another video, you've encountered a YouTube annotation. The feature let creators add content to their video after it had already gone live, but it had its drawbacks -- annotation boxes weren't dynamic, and the only worked on the desktop version of the site. Soon, they won't work at all. Today, YouTube announce that the feature is being retired. Instead, it encourages creators to use its Cards and End Screens features, which work equally well on desktop and mobile devices.