Evalute Websites

How do you know if the information on a website is correct and reliable ? I know if the information of the website is correct and the reason because of that is when you find some other websites that you need to do any kind of work that you do in class or even when you have a job. The websites that you've been going on are sometimes not reliable or in any of the computer systems so to that  when you have some kind of test that you need to look for some answers or if you halt to study then you got to use the websites that can be correct and not reliable.