As I do not wish to use the SD service of the shield, I thought I could simply ground pin 10 locally on the Ethernet shield, thus permitting the elimination of the separate wire connecting the number 10 pins on the two boards.
But this causes my web server to NOT work any more !
Even after cold reboot.
Manipulating pin 4 seems to make no difference.
Not sure what you have done or why, but if you do not have an SD card in the SD slot on the w5100 ethernet shield, then the operation of the ethernet shield should be unaffected.