Simple line following robot.

This is my latest project and one I wanted to build for awhile.Since this the first line follower I'm making I choose for a simple circuit:

I got the design from this source.It took me a bit of troubleshooting on the breadboard to make it work.

Even though this is supposed to be a black line follower,my motors stopped when the LDR's were covered.So it seems to be turning into a white line follower.