Each source should be evaluated to make sure the information is useful. Just because something is published, does not make it a good source of information.

External Validity: Is the website publisher or author a reputable source? Is the author qualified (institutional affiliation, degree)? Is the website endorsed by or linked from a nationally recognized organization? A "~NAME" in the address usually indicates a personal website with no official sanction. With many sites, you may need to trace back in the URL to view a page in a higher directory to find more background information. Sources from .EDU, .GOV, .ORG, or a state (.ca.us) are more reliable than .COM pages. Commercial sites are usually slanted to gain profit and present biased information. Recognized internet databases such as ERIC, PsycINFO, and Academic Search Elite are very reliable sources of information. If the database is available through a library and/or requires a paid service to access the information, it is usually a reliable source.

Internal Validity: Does the information agree with what you know about the subject? Does the lesson plan include information it should include? Is the information consistent with what you have found in other sources? Is the information current? Is the information comprehensive?