Conversion tracking is one of the hottest things in online marketing right now, as it allows you to track all those lovely visitors and which sources they came from before they bought a product or filled in your form.

However, anyone who has spend any time trying to compare the results of conversion from their Adwords campaign screen with the conversion reported by Google Analytics will end up scratching their head in puzzlement. This is because the results from the two sources are different.

I knew I had read about this in detail when the subject came up in conversation yesterday, and sure enough it was on the blog by those people at ROI Revolution. They explain in complete detail how this happens, and why neither measurement is actually wrong! 

In summary however, Google Adwords conversions tracks using the original visit to your site for up to 30 days, even if the visitor buys on a subsequent visit via organic search.

Google Analytics on the other hand, always tracks the last referrer, so the above example would be credited to the organic search and not to the PPC click.

The Adwords conversion tracking works in Adwords favour by retaining that person as a PPC click for a longer time. This effectively puts the Adwords conversions in the best possible light by tracking the user back to how they originally found you.

Conversely, the Analytics way tends to downplay PPC if the user returned to your site later (already knowing your company name) via natural search engine results.

So which statistics you want to use can depend on what case you are trying to make.