Since anyone can put whatever information they want on the Internet, not all web sites are created equal.
Some points to consider when evaluating the information provided by a web site:
Who is the audience for the information and what is their goal?
Is the information accurate and complete?
Is the information current?
When was the web site last revised?
Who is the author(s) or sponsor of the web site?
What are the credentials of the author(s) or creator of the web site?
Are there other online or print sources for the information?
This is an informative page from Cornell University on how to correctly evaluate web pages.