Sometimes, you'll come across a link that's dead or unavailable for some reason. Or perhaps you want to see what a particular page looked like a while ago.
The Wayback Machine from Archive.org, and Google Cache often have what you're looking for. However, copy-pasting the URL into those services takes time -- more time than I'm willing to spend, in any case -- and so now I've greatly speeded up the process.
For links on any page:
Right-click the link, then select the place you want to look under the "Previous versions" menu entry.
For the page you're viewing or a different page:
Right-click anything that's not a link, and under the "Previous versions" menu entry, select the service to look it up in. A dialog will appear with the current page's URL filled in for you. If you'd like to see a different page instead, enter its URL. Then, click OK.