As you may know, people around the world share knowledge that they know hopefully to help others in learning. However, while well intention, they may not be experts or know that exact situation or problem you face. So not all learning objects like web sites, videos, etc maybe a good fit.
So when searching on the Internet for Math help, ask yourself:
If it all checks out I'm sure you're good to use it as a source of information.
Information sources can be found online or in print, depending on how the publisher makes them available. This list will help you understand the benefits of using each of these types of sources.
Encyclopedias and Handbooks