Most are. Some controls, such as Label, emit simple HTML tags that are compatible with virtually all browsers. Others, such as Calendar, emit a mix of HTML and client-side JavaScript. Fortunately, that JavaScript is simple enough to work with any browser that supports client-side scripting. The exception is the validation controls, which emit complex JavaScript that integrates intimately with the browser's DHTML Document Object Model (DOM). Because the DOMs used by Navigator and IE are so different, the ASP.NET validation controls don't work with Navigator. They can still validate input on the server, but they don't even attempt to validate on the client in Navigator.