I found great extension Resurrect Pages that allows you to view cached versions of pages when the site is down or other way unavailable.
Dead pages, broken links, the scourge of the internet. Powerhouse sites like Slashdot and Digg can bring a server to its knees. What do we do when a page is dead but we still want to see it? Call in the clerics, and perform a resurrection…
Searches through five big page cache/mirrors:
o Google Cache
o Yahoo! Cache
o The Internet Archive
o MSN Cache