If this is your website you have failed and need to develop a website that is compatible with all major browsers.
I was using Firefox, which accounts for about 22% of users. Your website should be compatible with it.
IE only accounts for a little more than half of browser use. That means that half of the users that come to this site, see this warning. And just because the warning was posted, telling people to go use a IE, doesn't solve the problem that your website is poorly designed.
Signs, arrows, warning popup boxes, and other quick/lazy band-aids don't fix a poorly designed site.