title_body: Does the MOBI file format for Kindle use the same CSS standards as browsers?
upvoted_answer: Are there differences or limitations in how MOBI renders or interprets
    CSS?
  
  
  In a word - yes.  The CSS support for modern browsers is much much more extensive than the CSS support for e-readers.  There simply has not been the same level (or expectation) of standardization for the epub format, in general.  It used to be because of hardware limitations but now that mostly every e-reader has enough power it can really only be attributed to the negligence of the e-reader manufacturers.
  
  This site provides metrics for specification support by e-reader including the Kindles
  http://epubtest.org/rs/14/ and you can go specifically this page to see the stlyling support for the Kindle Fire http://epubtest.org/rs/14/.
  
  Also, in reference to your specific issue, the TOC is more difficult to style than the regular body matter because it is automatically generated and adds one more layer of obfuscation when trying to find out the code that is generating the style.