I was merrily using Time on Page and Time on Site metrics for quite some time before I actually realized how they were being measured. It was a real Doh (!) moment. Turns out we have not rfid’ed every visitor and they don’t rub their head against their monitor before starting their session on my website (and of course another head rub when they decide they have had enough and exit). This would allow us to capture the time stamps accurately and have exact measures. What a disappointment! Joking, just joking!! :) I find that few people understand correctly how…