Since i am a newbie,i have a problem regarding joining two common ground on the board.In this case the first led is connected to ground and some pin no. but the 2nd and third led,their anodes are connected to the pin nos. on the arduino board but their cathode is just left on the ground rail on the …

connecting two common ground on the breadboard to one on arduino?

fungus January 6, 2013, 9:15pm 5

codlink:
All grounds should be connected.

No, all grounds MUST be connected.