Since I really enjoy watching Youtube videos while zoomed in on my MacBook, using Ctrl + two fingers on the touchpad (or a scrollweel on an external mouse), I created Blacktube.

Blacktube lets you watch any video on a completely black background so you are not distracted by the text and other colors on the original page. All you have to do is copy the following bookmarklet to you bookmars bar and click it while on the video’s Youtube page.

• In Mozilla, drag this link to your link toolbar or right-click and bookmark it: Blacktube
• In IE, right click the link and then click “Add To Favories.” It will give a security warning, but this bookmarklet is safe to use. Choose a folder – if you have the links toolbar visible and choose the “Links” folder, it will be added to the toolbar: Blacktube

The resulting page will extract the movie you wanted to watch from the HTTP referer URL and display it on a black background leaving you with a completely quiet watching environment which is – in my opinion – very convenient for zooming in 🙂

Please give me feedback in the comments, on what to improve or if any bugs occurred, while using it.

UPDATE:
The blacktube.no-panic.at Domain and the bookmarklet aren’t active any more.
I’ve mirrored the code here for you to look at: http://stuff.no-panic.at/src/blacktube.phps