Select the size of the YouTube video player, center YouTube pages, and have two columns on the homepage.
Adjuster allows you to easily change:
• The size of the YouTube™ video player,
• Whether to center YouTube™ pages (homepage and video pages),
• Whether to display two columns of videos on the homepage.
Your preferences will be saved so you're choices are applied as the page loads.
The extension may not work if you are visiting YouTube via https://. Changing this to http:// should fix it straight away.