ads vary based on the content of the website not the person looking. If every time you look you see car ads, than other people are going to see car ads as well. don't know if thats what your asking. or as said before ... ask them lol.
use a adsense sandbox.. amit agarwal has coded a good adsense sandbox here http://www.labnol.org/google-adsense-sandbox/ also digital point's version http://www.digitalpoint.com/tools/adsense-sandbox/ [not good enough]
Thanks all for reply. @B'd www.labnol.org/google-adsense-sandbox is very helpful, thanks for sharing!
Ads vary mainly based on the number and "quality" of ads to be displayed which is based on the number of advertisers interested to advertise in a certain domain. High paying ads might not show on low authority web sites. Google usually pretty easily can make you a profile and customize what you see based on your profile. and this is only the beginning.
Of cource NOT. The NEW Google DART system displays ALSO ads NOT RELEVENT to the website, but related to what the user has been searching/browsing.
Ads also vary according to the location of the surfer. If you are in US you get US based ads and if you are in India you get India based ads.