Critically examine the websites you find using the following touchstones:

Where has the information come from? Has it been arranged conveniently? (Does it contain a history of the subject, an encyclopaedia, links to other organisations, a list of terms, etc)
Who is responsible? Is it clear (in Over/about or Colophon) who has set up the website ; is there an e-mail address or a telephone number available? If that information is not available there is a good chance that nobody wants to be held responsible for its quality. It’s better to look for a website that provide this information.
How current is the information? If it’s been one year or longer since the last time the site was updated, the information will already have lost its freshness. (You will often find the date of the last update at the bottom of the page).

Try to determine the purpose of the website. Is it to inform, or to entertain? Or is the main purpose to advertise about a certain product or service?
Is the person behind the website neutral? The website www.martinlutherking.org (about the famous black activist that was murdered in the sixties) for example, seems reliable at first glance. But at the bottom of the page you’ll see a link to Stormfront, a racist organization, that hosts the site! Big chance that this site is unreliable, especially with this topic.