An anonymous reader writes "I work in the marketing and advertising department of a small US-based manufacturing company. Last year I implemented Google Analytics into our website so we could get a better idea of what users were doing while on our website. However, sometimes I'll receive reports from other websites that we advertise with, showing the amount of traffic that they have sent our way. These numbers always conflict with my own data from Google Analytics. Is this par for the course with web analytics, or can this situation be rectified? This data is supposed to provide solid information when making marketing decisions and I need to know that I can trust it. I'm interested in knowing what other Slashdotters have done with their analytical data and the anomalies they have experienced."