<!DOCTYPE html> <!-- Any copyright is dedicated to the Public Domain. - http://creativecommons.org/publicdomain/zero/1.0/ --> <head> <style> details::after { content: "This is the details."; /* Match the margins and display of <p> */ display: block; margin-block-start: 1em; margin-block-end: 1em; } </style> </head> <html> <body> <details> <summary>Summary</summary> </details> </body> </html>