Whenever you are considering using a website as a source, it is very important that you review the contents in detail. An easy way to make a determination is to use Jim Kapoun's Five Criteria for Evaluating Web Pages:
There are many other resources to evaluate web pages. One of the more interesting examples is CSU Chico's CRAAP Test.
Limiting your search to specific domains (.edu or .gov) can remove some of the less reputable websites from your Google searches.
.com - commercial or business
.edu - educational institution
.org - organization (often non-profit)
.gov - government organization