How can I use this?
It seems obvious to state that no one is an expert at everything but it's easy to overlook an author's credentials - especially when reading something online.
Anyone with an internet connection has the potential to publish and distribute information - it's up to you to assess whether or not the materials you find have been written by an authority on the subject.
If you cannot find an author or an organization connected to a source, be very suspicious. If no one wants to stand behind the work, why should you believe what is written there? Even if you can find an organization or author you still need to be cautious and make sure that the organization and/or author are who they say they are. This may include further research on a particular author or organization. The website alexa.com lets you check ownership of a website and find out what other sites link to it. Also, note that even if an author is an expert in one field, she or he may not have expertise in another field.
Some materials that you find will be written by academics, for an academic audience - and their authority, accuracy and scope will be relatively easy to analyze and some will be written for a general audience - with qualities that are equally easy to assess.
Unfortunately, you will also easily find materials which are trickier to categorize, such as:
In fact, many of the sources which come up in a typical results list are not scholarly - and you won't be able to use them if your assignment specifies "scholarly sources only."