avoiding popup blockers

hi...

i have this problem...
i created a web site... in one page i save in a session var a byte array... and in that page i call a popup window, in the popup window i load that session var and print it...
Response.ContentType = "application/pdf";
Response.OutputStream.Write(var,0,var.length)

and it works fine.
but i published it yesterday in internet, and popup window wont open! iexplorer blocks it... with firefox 2 it works correctly but with iexplorer 7 doesnt, even deactivating iexplorer's popup blocker!
why could this be happening?

i think i could get this done also by opening a new blank window instead of popup but i dont know how to do it...

any suggestions?
thanks in advance...

All popup blockers block any window opened without user interaction. In other words they have to open by a link or onclick. If there was a way around this, then all advertisers and spammers would use those and then the whole point of having a popup blocker has been compromised.

yes...
i had to get it done by using a hyperlink button with a _blank target... instead of a window.open
thanks