By comparing the problem code I had copied from example in chapter 17 of "Beginning Arduino 2nd edition by McRoberts"
to the Arduino Example in "Examples\Ethernet\WebServer" I discovered the following:
//client.println("HTTP/1.1 200 OK\n"); // Standard HTTP response // no good with Firefox
client.println("HTTP/1.1 200 OK"); // Standard HTTP response
Nope this is useful for others doing a web search on the topic.