I've been looking at my headers the old-fashioned way with
curl -I and
wget --save-headers, but I notice Chrome and IE have some pretty advanced site diagnostics built-in now. Here I am using Chrome's F12 to check my HTTP headers which I just changed.
Whoops! I messed up those headers! I fixed them after I made the video, and then I used Chrome's F12 to check them, and this time I got them right.