Requiring IE is both foolish and dangerous. Anyone who is anyone in the computing world has migrated to the ease, features and relative safety of Firefox. ActiveX is just an open door to hackers.
The tab feature alone makes my slow dialup connection tolerable!
I routinely pass over sites that won't open with Firefox, figuring that if they don't need the business of the entire web, then they don't need mine.
I will send those letters, in the hope that the Copyright Office will come to their senses!
Who cares? IE is the browser standard.
One test for Firefox. Go to http://www.drudgereport.com
You WILL get a pop-up ad. I have an ad blocker and it works fine with I.E. but not with Firefox.