I have a relatively new site without much traffic from searches.
I have set up an Adwords account and an Overture account. In each case the url bears an account identifier i.e. www.widget.com?refer=overture or www.widget.com?refer=google. Last month Overture reported X clicks and google 2.5 X clicks. However, when I parse the server logs (Apache on a Linux box), there are 5-10 times more overture entries than Google and the Google entries are too few by far in relation to the clicks I have been billed for by Google.
Also, I have stopped the Overture account on a couple of occasions and seen traffic fall to about 30% of the Google + Overture volume. So the clicks/log descrepancy seems to hold up.
Is there a simple explaination for the descrepancy between the reported clicks and log confirmation? Has anyone else seen something similar?
We have tracking URLs set up for overture that actually write to a database when they are clicked on, and that number is always just a bit lower than the clicks that overture reports to us. Overture is probably lower because it is not counting resests that the DB is recording. Based on our experience overture has never over reported.
We do not run adwords so cannot help you there.
The problem might be in your log analysis. Referring urls are the shakiest set of data to work with, and a lot of times users will not leave a referring URL. Try seeing if your blank entry referrers are more than your missing overture and adword traffic. If it is then that is a place to start.