With wowhead's newer layout change, it leaves large areas of space on the sides of the page. As such the old functionality to click wowhead's built in "expand site" button is also gone. This will instead adjust the margin values. This extension does not block ads, it is merely a cosmetic change to the website. This is very lightweight and might be easily broken in the future if the website undergoes major layout changes. This extension only activates on wowhead.com.
