I spent a lot of time looking for these problems and found the following:
- I had bad (old) code in a customized jacket. This is where the
Code:
-webkit-border-radius:8px;
was coming from.
- The empty stylesheet declarations are generated by calibre's built-in jacket builder, not this plugin. The calibre editor flags them as errors, but epubcheck doesn't care about them. I have a possible fix I will send to Kovid.
- The "data-calibre-jacket-searchable-tags" (non-)error is explained in the post above.