It appears that Yahoo has joined Gigablast and Clusty and is now providing direct links to "archived" versions of pages via The Internet Archive's Wayback Machine. You'll find a direct link to check to see if older versions of the page are available in the box at the top of every page that Yahoo caches. Look for the text link that reads, "check for previous versions at the Internet Archive." Click the link and you'll transported to The Wayback Machine to see if older copies for the page/URL you're viewing have been archived.
Introducing SES Online
Want to view one of the sessions you missed or listen to an especially informative presenter a second time? SES New York sessions are available for purchase on ClickZ Academy's new e-Learning site. SES is now Online!