Using websites can be tricky. Ask these questions to get a sense for whether the website is reliable:
Ask who is responsible for the information. Are they qualified to teach you? Why are they providing this information? Does someone take credit for the information by name? Can you contact them if you have questions?
Ask whether the information is objective. Does it present both sides of an issue? Is it designed to persuade you? Does anything about the information seem fishy?
Ask how current the information is. Is the site dated? Has it been updated recently enough to provide good information? Are there old or out of date links?