My thinking was that if a user wanted to override any css files included in the new html header it would *just work* if the css was included below the inserted html header.  Otherwise any css included would overwrite the custom css.  They could force their css to be used by using !important in their definitions, but seems less ideal.

I may be wrong about how css inheritance works, I am not very experienced in the area, but that was the rational.  I think I did test both options before submitting the patch, but it has been a while, so I could be mistaken.