Just recently, say in the past year or so, I have noticed an increasing number of sites that do not work as intended in Firefox (my browser of choice for a long time), and instead I have to open these in IE.
You used to see this a lot many years ago, but I thought those days were supposed to be over (standards, anyone?) At least back then, you got a message saying "this site is optimised for IE 6.0' (!!!!), but now you don't even get that - sometimes the input boxes and other controls simply just don't display. We're going backwards.