Dead pages, broken links, the scourge of the Internet. Powerhouse sites like Slashdot and Digg can bring a server to its knees. Features include: Searches through five big page cache/mirrors: CoralCDN; Google Cache; Yahoo Cache; The Internet Archive; and MSN Cache.
Of course, not every page can be in every cache. When a page is unavailable, you'll generally see that site's error page. Hit back and try another one. Also, extension is accessible thru: In the context (right-click) menu for the current page, and for all links; In the toolbar, just customize it to drag the button in; and With the keyboard: press Ctrl-Shift-U.