Web developers: when you say, “your browser does not support this site,” what you REALLY mean is that YOU don’t support the browser. Don’t turn it around on the user because you chose not to stick to well-supported standards, or worse, are doing user agent sniffing.
If you truly use some feature shipped by one browser and not everyone, at least say, “We use x standard feature, which is unsupported in this browser.” But even then, the web is all about progressive enhancement.