Invisible content

What makes the content of this web page http://nuclearinfo.org/view/item/a2156 (which is allegedly W3C checked, and doesn't seem to have any serious syntax errors reported when you test it there) invisible on NetSurf when you view the page on their servers, but visible if you save the HTML and double-click on it locally? (CSS, presumably?) -- Harriet Bazley == Loyaulte me lie == Anything can happen in the next half-hour....