After doing a Google search have you ever wondered if you will see the exact same result in another web browser?
You really should, but this is not always the case. There are a number of different factors involved. If you are signed into any Google type of account such as gmail, analytics, webmaster tools, adsense, blogger, etc. Google tends to track your browsing history. If you search for something and decide to click on a link it Google will track that. If you repeat the same search later and say you click on the same link again, over time it will start to move up in the search results but just for you and your web browser.
Sometimes what happens is you are logged into Google and you start searching for your site to see where it shows up. Then you click a few of your links lets say. Then all of a sudden it appears that you have moved up in the search results.
I don't know how many times people have told me that they rank #1 or #2 for some search keyword or keyphrase. When actually it is only because their particular web browser is remembering and tracking their activity. I suggest making sure you are logged out of any and all Google accounts, make sure web history is not enabled and repeat the same Google search. Most people will find that they are no longer #1 or #2.
If you really want to see where you really rank, you should be logged out of Google but also verify that Google still isn't remembering your browsing history while logged out.
You might still be ranking well, but it is always best to be logged out of Google for most accurate results.
Watch this Matt Cutts from Google video for a little more input if interested.