Evaluating websites is an important skill, and is not an exact science. You will need to look at a variety of criteria before making a decision about using a web resource. Also be aware that some resources may be appropriate for some research needs, but not others. There is no one simple short cut for determining the veracity of a site. You will need to put your critical thinking skills to work!
The domain, or suffix, of the site is one of the first things you can look at. Any of these are potentially biased. Familiar domains include
.com - A commercial website. Some students have been given blanket rules not to use these as commercial influence may effect the content of the site. However, many credible sources, including some peer-reviewed sites, use this domain. Do not dismiss these out of hand.
.edu - A site sponsored by an educational institution. Just as .com sites should not necessarily be dismissed .edu sites should not be given an automatic pass. A site with this suffix may be a personal website that is simply hosted by the university. Additionally, colleges and universities with religious affiliations can use this domain. Consider how the religious viewpoint may effect the site's content before deciding. Beware of websites with the suffix edu.co. These are likely commercial sites.
.gov - A government sponsored site. Again, be aware that government policy can be influenced by many things including public opinion and lobbyists, and not necessarily on evidence-based research. Statistics on these sites are usually accurate, however doing a little extra research will go a long way. Remember that the government of the state of Michigan told the residents of Flint that their drinking water was safe! Government sites are generally good for finding current laws, tax codes, and forms.
.mil - A military site. Caveats are the same as for government sites.
.org - An organizational site. Some educational institutions may use this as well. These may take a little extra research. Look for more information about the organization to determine what bias it may have. For example the National Rifle Association's website can be found at nra.org. If you want to research the National Rifle Association, or become a member, this is likely a good site to look at. However, if you are looking for unbiased information about gun control you may want to do some more research.
.net - There are no restrictions on who can host these sites.
Does the website indicate when it was published and/or updated? Old information may no longer be useful, or it may be what you need for a historical perspective.
Can you find an author's name and affiliation? Does the author provide contact information (via e-mail, phone, or social media?) What are the authors' credentials? Do they have a expertise in the field they are writing about. A well-respected professor of English literature may have a cooking blog. Unless she also has expertise in nutrition the blog may just be a hobby.
Read the content! If something seems implausible, or too good to be true it probably is. Do some extra research.
Be aware that a website's author, editor, and publisher may know all these tips for evaluating sites, and therefore may be working to ensure that the site looks legitmate. The Northwest Pacific Tree Octopus site has current dates, links that work and an author with a (fake) affiliation. Always look for more information if something seems implausible!