Holy cow!! There are two of you?? Digital pin 4 is the SD SPI control.
In the current arduino librarys developed for hardware interface, it appears that pin 10 is used for spi interface with an ethernet shield and pin 4 is used as the interface pin for an SD device. Have you actually tried compiling the code I posted? If so, what errors do you get? Just to minimize potential future issues when SD cards are actually being used, I'll change the test pin to 5 or similar. 
Frank knew that no man had ever crossed the desert on foot and lived to tell about it. So, he decided to get back in his car and keep driving. - Deep Thoughts by Jack Handy