Can I use an LED in place of a diode?

I don't know much about this electronics stuff, but I am about to assemble the relay circuit in the following diagram. I want an LED to show that the relay is energized. Can I just replace the diode with an LED?

-Valkyrie-MT

This is the schematic I am referencing:

http://www.arduino.cc/playground/uploads/Learning/relays.pdf

-Valkyrie-MT