I recently have begun learning how to read the tape. On Friday, 061501 (triple witching) I was watching the tape on DIA. I noticed that in the last 2 hours all of a sudden a big order, 50k would hit the bid....the rest of the orders would be around 100 to 2k shares...some hitting the bid....some the ask...a few minutes later the DIA would drop. I saw this take place numerous times...a few shares then another 20k hit the bid....and the DIA would drop. Now I know that the DIA tracks the Dow so I don't understand how what someone sells on the DIA would make any difference on what happens on the DOW. But it was very consistent in the last 2 hours on Friday. Is this related to triple witching? Can someone please explain what possibly is taking place? TIA, Kevin