where is the page at?
I use a delay on my jquery to accomplish stripping out the elements when I customized the html player.
one part of it, I copied the css code, but on the dynamically loaded css file that loads with the player, I made it delay for a second so it executes the jquery css changes after it loads its elements.
My site is at knkl.net so if you want to see a re-skined html5 player.
If the css is in a file that you load on the web page, then copying that file locally and altering the css would be the preferred method. otherwise, you have to change the css attributes using jquery after it loads.