lucy24 - 7:03 am on Jun 2, 2011 (gmt 0)
not sure where Laura has gone
To bed, probably, if she's posting from England.
I looked more closely at my own Firefox prefs and immediately came across the "add-ons". Is it possible that the troublemaker is not Firefox itself but some unsuspecting or unsuspected extra? I don't have any myself, but I assume there's some way to disable them and check for a change in behavior. Is everyone using the same version of Firefox? Or, at least, is one of the other computers using the same version as yours?
The CSS is indeed perfectly lovely and validates a treat... but have you taken a closer look at the html? Gazillions of errors and warnings, not all of them attributable to unclosed tags. Was it originally written in some other (X)HTML and then changed? XHTML tends to throw fits about things that are perfectly normal in HTML.
:: irritably wondering when the CSS validator decided to abandon yapping about "color" without "background-color" and vice versa, now that I've utterly internalized "background-color: inherit" just to make it happy ::