web usage report

Hi all,

I'm trying to generate a report on web usage for some domains. However, we find that the report is not precise and accurate. 

Let's say I want to generate a report to see who have visited facebook.com

In a controlled environment, I would use userA as an example, userA only visited CNN.com but because CNN has embedded links to facebook.com or any marketing, statistic related tools on CNN.com,  userA would show up on the web usage report on facebook.com when I filtered down the report.

When I look closely at the web protection log,  any request to *.facebook.com  (* can be anything) would make the user show up on the web usage report for facebook.com

This does not provide an accurate report as to who actually visit facebook.com.

Does anyone have a way to create a more accurate report?

Thanks,

MT