School librarians help their students learn to search the Web and evaluate websites for validity. Check out these sample lessons from informationliteracy.org:

The Good, The Bad, and The Ugly: Students are given a lesson on how to judge the accuracy of a website and if it should or should not be used for research.

Of Course It's True, I Found It On the Internet: Students learn why it is important to evaluate sources of information, and criteria to use for evaluation.