I had a hard time deciding whether to ++ this node or not.
Clearly, the specified file: URI tells the web browser to read the file from its local hard drive, not from a remote server. But your example of a good test case for CSS is spot on (simple and obvious!). These two came up to a draw.
Ultimately, your signature line won me over, so ++! (For some reason at work, my rxvt windows keep losing echo, usually when breaking out of a command | more pipeline, and I have to type stty echo to correct it.)