https://en.wikipedia.org/wiki/Template:Hidden
https://meta.wikimedia.org/wiki/Template_talk:Hidden
A “show/hide” button for a block of text.
Copy and paste the appropriate content from [[MediaWiki:Monobook.css]] and [[MediaWiki:Monobook.js]] and then use this feature like this:
<div class="NavFrame"> <div style="background: #ccccff" class="NavHead">Optional header text</div> <div class="NavContent" align=left> This text is hideable </div> </div>
You can also put that into a template and re-use it without needing to make <div> tags. [ 1 ] An intelligent wiki administrator should ban the use of <div> tags in templates.
Footnotes
| ^ 1 | An intelligent wiki administrator should ban the use of <div> tags in templates. |

ported