I don't know what I've done, but I just posted my last entry and some of the style information has vanished! All the background colours, link-styles are gone, but the sizes of all the elements and the locations of all the stuff are still intact.
Just typing this it's occured to me… in the Blix theme (and I'm assuming most others; I'm VERY new to WordPress!) the general page layout and the page colours etc are in two seperate CSS files, so perhaps the layout CSS is fine but the 'flavour' CSS file isn't.
The question is though; why would the flavour CSS file get corrupted simply by posting an entry? This is probably my lack of WordPress experience speaking… but I'm baffled.
Operation WTF has begun.