First, it's important to know that websites ending in ".com," ".org," and ".net" are available for purchase, meaning anyone can publish content on these sites, regardless of knowledge on any particular topic. Typically, it's best to evaluate sources ending in a ".edu" (designated for educational institutions) or ".gov" (designated for governmental organizations) as being more credible than others you might find. Of course, we've all probably looked at websites ending in ".edu" only to find a teacher's third grade class's research papers or have visited an organization such as National Geographic, which is quite valid and does end in a ".com." Therefore, these address endings aren't hard-and-fast rules but are a good starting point for your evaluations.
After checking the web address, consider the author of the information. Is he or she an expert in the field? Does the author provide educational background or work experience in some sort of biographical link? If you can't even find an author listed or if there is little to no information about the author of the information, that's a red flag about the credibility of that information.
Also check the date of publication. This is typically found near the bottom of the web page in small print. Of course, you really want the most updated and current information possible when researching, so if the information was published in 2012 and hasn't been updated since, that could really weaken the credibility of your information. For some topics, this makes a bigger difference than others. Consider how much information has changed about social media, for example, since 2012. An online article about the impact of social media written eight years ago is not going to provide the most relevant information today.
Does the article seem to be written from an objective point of view? Or does it present a clear bias? You want to gather information from sources which allow you to do your own evaluation, not rely on sources which are clearly presenting only one side of any particular argument. Cross-reference information you find to be sure that the information seems accurate based on other research.
Does the author provide her own footnotes and links to research presented in the article? Doing so greatly increases the validity of the findings. If you can follow the trail of the author's research, that shows that she is being intentionally transparent.
It's also good to check for paid sponsorships affiliated with the posted research. Of course, an article written about the effects of germs and sponsored by a major cleaning brand might have monetary gain as its primary goal, not completely unbiased information.
I hope this helps as you evaluate online literature. Good luck!