They are similar to conference papers. World Wide Web sites can be the most difficult to evaluate. Informational Web sites often end in .edu or .gov , relating to educational or governmental sources. Sites ending in .org , organizations, can also be useful. Their main purpose might be advertising.
Currency is a most important criterion for a Web site.
Primary sources usually present an idea or hypothesis, a research methodology, data or arguments to support the hypothesis, and conclusions about the results. If the source is not describing the results of empirical research, then it must present original material, or a new interpretation of previously published ideas. Secondary sources gather together primary information to review or evaluate it, or to present an overview of the subject. They often provide access to sources that are difficult to find. Secondary sources serve a practical purpose in providing background information and a synthesis of the information or directing the researcher to additional information.