Web sites are all created with a purpose in mind, this can be to educate, inform, instruct, persuade, sell, or to misinform.
Web sites used for educational purposes should have the primary goal of education or informing individuals.
You can use sites that were not created primarily for educational purposes but still need to evaluate the site and if there is bias you need to be aware of this.
Anyone can self publish on the internet; it is important to determine if the individual publishing is qualified to write on the topic and that their work reflects quality scholarship and accurate information.
There should always be information on the creator or contributors to a web resource. This may be an institution or a group of individuals.
The information provided should be neutral and statements should be supported with legitimate evidence or research.
The information provided should be updated regularly and reflect the newest knowledge in the field whenever possible.
The website should cover the specific topic in a comprehensive a thorough manner.
You will need to look at all of those different elements of a website in order to determine if it is a good source.