THere are lots of ways cookies can “crumble” (groan)
Users can turn them off.
Users can be using non-IE browsers that some casinos do not support.
Cookies can be cleaned on a daily basis (by user software).
TRACKING TESTS
as for tracking – I track each click out of my site by destination – and compare them to the casino clicks count.
Most of the sites that I use validate to a 95%-99% level (otherwise I would not use them) and that missing percentage could be reasonably assigned to internet issues.
– perhaps a DNS error or page not appearing
– or user clicking stop/back button (didn’t want to go there)
– or user closing window
I don’t think I would ever expect to tally past 95-99% of clicks.