Mozilla CSS glitch?

I've got a page that calls

<link href="/structure.css" rel="stylesheet" type="text/css" />
<link href="/skin.css" rel="stylesheet" type="text/css" />

Occasionally, when I'm viewing the site with Netscape or Firefox, the text in
one of my tables fails to get the proper font size. Reloading the page fixes
this. At first I thought it was a matter of caching, but if you navigate away
and come back it happens (intermittenly) again.

Does anyone know of a specific issue that may cause this?

Thanks!