I see this error message in the FireBug console: "Expected color but found 'thin'. Expected color but found 'dotted'. Expected color but found 'invert'. Expected end of value but found 'invert'. Error in parsing value for 'outline'. Declaration dropped."
It is complaining about this line in w3-html40-recommended.css:
The issue is using 'invert' to describe the color. This is a Mozilla "Won't Fix" bug. See https://developer.mozilla.org/en-US/docs/Web/CSS/outline-color#Browser_compatibility, which also shows that Chrome doesn't support the 'invert' color value. The solution is to pick a specific color. I will pick black.