Who? Is the author of the site a person or an organization? How do I know I can trust them? What qualifies them to share/report on this information?
What? Does the website make any claims that need backed up with evidence? Am I finding the same claims in other places? Does the information have any bias?
When? When was this page last updated? Is this time-sensitive information?
Where? What type of URL is it? Is it at a .org, .edu, or .gov? (Return to Who? if uncertain about whether you should trust a URL)
Why? What is the purpose of this website? To inform? To persuade? (Return to What? if uncertain about the information)
Use good sense when looking at a website. If it looks like some random person slapped together a Word document and put it online at a .net, chances are it's not worth using! Look for grammatical errors, pop-ups, and other general design for indicators of whether it is a professional/information website.