The HTML5 Details Polyfill WordPress plugin adds fallback support for the HTML5 <details> and <summary> elements in browsers that don’t support them using Mathias Bynens’ <details>/<summary> jQuery plugin.
Once the plugin is activated on your site, the following HTML should work in all modern browsers, even if they don’t natively support the <details> and <summary> elements:
<details> <summary>Click for more info...</summary> This is where you'd add the additional content that won't be seen until the "summary" is clicked. </details>
Click for more info…
This is where you’d add the additional content that won’t be seen until the “summary” is clicked.