Google and YouTube are always tweaking. One new tweak is YouTube's browser view layout.
The YouTube Watch Page also has a new layout. The watch page URL is usually in this format http://www.youtube.com/watch?v= 'video id' and it is the final resolving location where a YouTube video can be viewed by the user. The Watch Page is is controlled by YouTube. This article discusses the Watch page from a traditional browser (not from a mobile or TV device).
You will notice right away the lighter background of the new Watch page design - but there are many other diferences. Below are screen shots of new and old.
|The new test design YouTube Watch page viewed from Chrome|
|The current YouTube Watch page viewed in Safari|