Help: Superhouse #12 - Home Automation Controller

So, I re-created Jon’s Home Automation Controller from his Superhouse #12 episode, and I’m running into a big issue. I uploaded the program onto the EtherTen, and when I load up the web server and toggle the outputs, nothing happens and the D13 pin on the EtherTen flickers with its red LED. Now, the red LED stays on permanently now, and thus is this causing my program to not work? I don’t really understand what the function is of the D13 pin.

Thank you for your time.