Phantom Gorilla 3.0 is a style for K2 — the versatile theme for WordPress.
PG3 is compatible with (to the best of my knowledge): Safari 2+, Firefox 1.5+, Opera 8+, Google Chrome (all versions) and Internet Explorer 6+. There may be more, but these versions were known to be working during testing. It does not, of course, look exactly the same in each one.
PG3 is not freely available. A tremendous amount of time and effort has gone into its development, and I’m not willing to give it to just anybody! If you wish to consider licensing it for your site, I suggest you contact me. There may be a modest fee.
You could just pinch the CSS from source, but it’s a specially customised version so you'd have a lot of work to clean it up. I suspect it’d be easier to talk to me.