The Internet has a lot of great information, but it also hosts untrue or biased information. Make sure your sources are credible.
Who is responsible for the information?
Is the information biased?
What is the purpose of the information?
Is the information up to date?
Is the information well documented?
Is the information relevant?
Wikipedia is a helpful site, but it isn't a reliable source for academic research. Wikipedia, and other websites that allow collaborative editing, may or may not have credible information--it isn't always easy to tell whether its credible or not. The editors may be wrong, they may not have the most up-to-date information, or they might even be vandalizing an article.
Where Wikipedia might be useful is at the bottom of the page. Sometimes you can find links there to primary documents and other sources.
Just for fun, here are some examples of Wikipedia vandalism. Don't let this distract you for too long.