Is there something about using a a style sheet to create hover links that doesn't work with a Mac?

My hoverlinks work great on PCs, but on my graphic designer's Mac they don't work properly.

Basically, the hover aspect doesn't work except on visited links. In other words, an unvisited blue link stays blue (instead of turning red) when hovered, but a visited purple link turns red when hovered.

I've attached the CSS file. A sample page is

Thanks for the help.