<!DOCTYPE html> <!-- Any copyright is dedicated to the Public Domain. - http://creativecommons.org/publicdomain/zero/1.0/ --> <html> <style> div#details::first-line { color: blue; } </style> <body> <div id="details"> <span>Summary <div>Block in summary</div> </span> <span>This is the details.</span> </div> </body> </html>