Too many Browsers?

Here at Egnyte, we are obviously heavily dependent on the browsers available in the wild. The trick is to support older browsers (but not too old) and new browsers (but not too new).We can get away with not supporting IE5 but for all its warts we do support IE6. On the other end, we can watch Chrome as it wends it way into our user base (or not). In an ideal world one could just support standards and test with reference implementations and not worry about all the browsers out there.Nowadays, java script quirks among browsers is fairly well handled by mature Ajax tool kits so that is less of an issue. For a performant application, we also have to pay attention to caching content in the browser and for support for plug-ins such as flash and applets. For caching we love the way "the best browser in the world" (safari) hangs on to content aggressively by default. But the only sane way out is to generateunique URLs by version rather than relying on HTTP headers.Then there are less used standards out there such as P3P for privacy. Some instances of our browser clients are embedded in larger applications. IE for one wants to see these special headers before it will hand off the request to the enclosing application.