Export as website: CSS font-size

It’s a great feature to export a folder with rtf-files as a website. But font-sizes in the website.css are set in pixel. I’d rather like to have relative font sizes set in em or percent. Is this possible?

No, that’s not (yet) possible as the website export plugin tries to rebuild the original rich text layout. But assuming that you’re always exporting the same documents, you could export them once, modify the CSS sheet on your own and then lock it via the Finder.