Navigating to https://www.tradeking.com/ causes a JavaScript dialog to be displayed claiming that Safari is not one of "the latest browsers".
I don't see any warning message. After spoofing UA as Konqueror the message appears: "TradeKing.com is best experienced using the following browsers and versions: Internet Explorer version 6.0 or higher (PC), Firefox version 1.0 or higher (Mac and PC), Camino (Mac), Safari (Mac, PC, iPhone), Mozilla version 1.7 or higher (Mac and PC), and Netscape version 7.2 or higher (Mac and PC)." So the bug is already fixed.