Information from web sites can be very easy to find. Due to the nature of the web, it is very important to evaluate anything that you find before including it in your assessments.
Anyone can author or publish material on a web site. No quality control process is required. This doesn't mean that you shouldn't use information from web sites! you just need to apply evaluation criteria to understand;
Authority - Who is the author? What are their qualifications and are they experts in the field they are writing about?
Objectivity - Is the purpose and intention of the source clear, including any bias or particular viewpoint?
Accuracy - Fact or opinion? What evidence is presented? Is it original research or copied from other sources?
Currency - When was it published? Has the field changed since it was published or last updated? Is this article relevant to your research?