It is important to evaluate all information you encounter, but it is especially important to be critical of the information you find on the web. Does it pass the CRAAP test?
Currency: Is the site up-to-date and edited regularly?
Relevancy: Who is the intended audience for this information and is the information unique?
Authority: Who is the author and what are his or her credentials? Is there contact information? Is it a company, organization, or university?
Accuracy: Where does this information come from? Are there sources listed? Are there typos or spelling or grammar errors?
Purpose: Why was this site created? Is it intending to sell a product? What is the domain name (.edu, .gov, .com, .org)?