The transitional XHTML 1.0 DTD has the br element with a default attribute of clear:none
The strict XHTML 1.0 DTD has the br element with no default attributes.
Double-checking the ePub specs, it seems we ought to be using the XHTML 1.1 DTD instead. And in that br has no default attributes.
So I think that epubcheck was right!
Originally Posted by charleski
It's nothing to do with your css.
You're using the transitional xhtml spec in your doctype:
Change that to
and the errors should go away
For instance, here's Pauls example ePub in which the only thing that's changed is the xhtml spec in the doctype. It now produces errors in epubcheck.