For anyone who is interested in tracking usage of their client web sites, I highly recommend GoSquared (http://www.gosquared.com).
Any, if you want to go beyond the simple everyday stats, you can use the API to track events, users, etc. (https://www.gosquared.com/docs/api). Requires programming skills.
Northern Penguin Technologies
"Any sufficiently advanced technology
is indistinguishable from magic."
........Arthur C. Clarke