ClickZ editor Rebecca Lieb takes a look at the silly conventions used in standard web metrics, which together contribute much of the difference between reality and web statistics. Among the fudgy perpetrators are assumptions about session length, a presumption that people don't share computers without logging out, the quaint notion that people turn off their computers and the completely unfounded speculation that a subscriber accessing from work will log out and then log back in with the same user ID from a home computer.