>>ill-mannered Websites out there!<<

I can only speak for myself here, but I should point out that in a non commercial setting, it's impossible for one to check all platforms. In our house we use unix as our operating system, (sometimes mac, but not regularly) and any product with microsoft printed anywhere on it is strictly forbidden to enter. This in mind, it is quite difficult for me to fully check my own sites on many browsers.

Another point could to be made is that it could be quite expensive and time consuming to assemble all the possible combinations of hardware and software. I have simply learned that quite often mainstream software does not work for my system. I give more merrit to those sites that take the time and effort to consider my platform.