Evaluating the sources of your information is a part of media literacy. You should apply evaluative criteria to all the sources you use in your research.
Questions to ask when evaluating media sources:
Who is sending this message and why?
What techniques are used to attract and hold attention?
What points of view are represented?
How might the message be interpreted in different ways?
What is omitted from the message?
Questions to ask when evaluating information from Web pages and other media sources:
What is the domain of the page?
Who is publishing or sponsoring the page? Is contact information for the author/publisher provided?
Strip back the URL to discover the source of the page.
How recently was the page updated?
Be particularly wary of bias when viewing web pages. Anyone can create a web page about any topic. YOU must verify the validity of the information.
When you have finished answering these questions, you will have a good idea of whether the website/media source is reliable. There is no single system of evaluation of media sources. See the Library 101 Research Guide page "Evaluate Your Sources" for more information.