Hi Wolfiesden,
Thanks for your demo code.
This is just what i have been looking for, well nearly!
I am very new to the Arduino and C and and trying to run before I can walk, like most newbies 
My ambition is to have a Web server running on the Arduino, my problem is that I want to change a graphic on the client when an input is switched on or off. e.g an LED switching from RED to Green.
To further complicate the issue i would like to have a couple of JPG or PNG pictures on web screen as well.
So far i have been able to call a web page (INDEX.HTM), with JPG and PNG graphics being called from a SD card on the Ethernet shield. This give me the rich look i want.
I have many examples of writing to the client directly from the program, as in your example, what i cant figure out is how to combine the two.
The issue I keep on hitting is the that the WEB server libraries cannot serve PNG or JPG file to the client.
I have found the TinyWebServer.H library which almost does what i want but being a newbie i find it difficult to see how to fully use it.
I am looking at using JAVA script to possible help solve the issue but this is adding to an already steep learning curve.
Any pointers on how to crack this would be greatly appreciated.
Many Thanks in advance
Ray
PS keep up the good work