Check your website for un-biased results in Google
Google will change its results based on what you have clicked on, and how many times you have clicked, especially if you are logged in to Gmail or another Google service while searching Google.
Google is trying to help you find the results you want, or at least what it thinks you want. Fine for general searching, unless you are checking your website results!
To get un-biased results, you need to turn off cookies in your browser, and logout of Gmail. As this is probably quite inconvenient, I suggest using a second browser such as Opera (free, www.opera.com) and make sure it removes all cookies when closing the browser.
This will give you clean, un-biased results in Google for checking your website position.