Google tailors all search results to the user. Pretty much, unless you are using a completely clean computer, freshly installed browser in an untraceable location, everyone will have the results they see in Google tailored to their person. Most of the time, you will not even notice how it is done. Overtly, you can tailor your search experience by blocking domains or selecting safe search. Covertly, Google will pick results it thinks you are likely to want to see. How does Google do this?

1. Search history. If you have visited a website before, Google will automatically move that website further up the pile. It might not be number one, but it will probably be moved to the front page.
2. Google+ friends. Got writers in your circle? They will be move to the top of the pile.
3. Location. Google will detect your nearest city, and then move pages with location information to the top of the pile.
4. Your browser. Using a mobile device? Google will select results that are tailored to your device.
5. Search history pt 2. Been searching for “Rome Holidays” and then switch to “Italy Hotels”, there is speculation that Google will use session based browsing behaviour to start bringing up more “Rome Hotels” as that is what you have been searching for in the past.