That's what I used to do, amyg - but it no longer works:
With this version of InDesign, it adds
your CSS document to InDesign's automatically created CSS, instead of replacing it. So there are two .css documents, both linked to all the XHTML documents. It does this even if you click the option not to create styles - then it just creates a much shorter default style sheet with rules for body, div, and all images.
So if you are clever you can write the imported CSS in such a way that they overwrite the InDesign version but I cant always figure a way to do that.
But my problem is not really with the CSS generated - I can always replace that. It's with the class references in the XHTML document. Because they get duplicated in this way, unless I do a regular expression find and replace to change them all to the same class reference, I would have to write a style for each of these duplicated classes, that are actually the same
Possible to do, but it's so messy!