Today, I came across http://music.twitter.com. Naturally, I inspected the HTML source just to see if there were any :hidden gems. There were none, bar one curious line of code that caught my eye. The image for the 'Sign In' button linked to the /_login/ directory — and so my journey began. background: url(/_login/btn-login-states.png) no-repeat 0 0; When I visited /_login/ I was presented with a p