•   Why was the site put on the web? Usual reasons include to:
   
  •   Inform  http://www.consumerreports.org/
     
  •   Sell  http://www.walmart.com/
     
  •   Share  http://www.dogbridge.com/
     
  •   Persuade  http://www.smallstep.gov/index.html
     
•   Does the site display advertisements?  If so, what types of advertisers does it allow/use?  (Load the page a couple times to check.  Often random ads will display for each page load.)
   
•   Look on the site for these links:
   
  •   About Us 
     
  •   Philosophy 
     
  •   Background
     
  •   Biography
     
  •   Who Am I?
     
  •   Example: http://www.webmd.com/ (About WebMD)

Now, use IMSA's 21st Century Information Fluency Project to view more ideas on this subject as well as quiz yourself.  Once at IMSA's MicroModules site, click on "Bias".
 

Finally, take a look at some examples in the light of this information.