No matter where you find your information, it's important to evaluate it. Even if it's information from a primary source, the primary source may have an agenda of its own, and if it's a primary source that is later posted online, does the entity that posted it have its own agenda? Have they posted the document in its original form, or has it been modified?

Some additional rules of thumb for evaluating information are available in Rampolla's Pocket Guide to Writing in History, 9th edition, on page 23. Here is a condensed version:

• Is it clear who wrote the material? What are the author's credentials?
• Are there references for the author's claims?
• Who produced or hosts the information? Is it from an educational institution, a government source, or a scholarly publisher?
• Can users change the information on the site? 
• Why is the information published? What's the motivation of the author and/or publisher?
• Can you corroborate the information with other sources you have?
• Does the information fit with the time period you are researching? Is it recent? Is it up to date?
• If the site links to other sites as support or as supplementary information, are those sites reputable?

You may also want to use the CRAAP Test, which you may be familiar with from other classes. A link to the CRAAP test is below.