When I export a CS6 InDesign document to html format I set the options to embed the CSS. But, I still get an external css file created. Why is this?
Because that's just the way CS6 works. When you export HTML or EPUB, even if you add your own CSS, a least a stub of the InDesign CSS is exported too.
Thanks for this. It must have changed from CS5.5 because it worked as expected in that version. Ask for an embedded CSS file in CS5.5 and the css rules got written into the htm file.