From Law Technology News: "Authenticating Web Pages as Evidence," by M. Anderson Berry and David Kiernan--
Plaintiff sues your client, claiming that his injuries have significantly affected his lifestyle. He is unable to work, travel or bowl. Not surprisingly, his spouse alleges loss of consortium. On the eve of trial, you discover pictures and other details on a social networking website about plaintiff's recent trip to the International Bowling Museum & Hall of Fame, including a picture of plaintiff proudly holding a fluorescent orange bowling ball and a four-foot tall gilded trophy dated four days earlier. As you approach the witness with printouts of the web pages, you are stopped in your tracks: "Objection, lack of foundation."
This article contains for authenticating web pages and Federal Rule of Evidence 201, 901 and 902. It also has an interesting section about court cases involving the Internet Archive or "Wayback Machine."
Related post: "Using Emails in Support of Summary Judgment or at Trial."