When using the web for your research, you want to evaluate whether or not the site contains reliable information. Use your better judgment, but don't just cite the first website you find. Here are a few questions you may want to ask yourself before using the information:
You can add certain terms to your Google Search to get more specific results.
Only looking for a PDF or a PowerPoint? Add filetype:pdf or filetype:ppt
Only want to find results from a Government or Education website: Add site:.gov or site:.edu
Only want results from one specific website? Add site:autismspeaks.org
Check out Google's Refine web searches page for more ideas on how to make Google work best for you.