While I tested the WebServer example with Firefox 3,
the browser often displayed an error message below.
"The connection to the server was reset while the page was loading."
So, I added a very simple code to the WebServer example like this;
delay(1); // added line
client.stop();
After this modification, I 've never seen the error message.
Probably, because the web server disappears too fast without any delay,
the web browser reports protocol violation.
The delay time seems to be sufficient only 1ms.