SandboxCss

This is the header cell, which is always shown
This cell is not shown by default.

Simple example

You will need to create three div elements:

<div class="NavFrame">
  <div class="NavHead">[... This is the title of your collapsible content ...]</div>
  <div class="NavContent">
    [... The content you want to hide goes here ...]
  </div>
</div>

[... This is the title of your collapsible content ...]

[... The content you want to hide goes here ...]

To initially hide the content do this:

<div class="NavFrame collapsed">
  <div class="NavHead">[... This is the title of the hidden content ...]</div>
  <div class="NavContent">
    [... This content is initially hidden ...]
  </div>
</div>

[... This is the title of the hidden content ...]

[... This content is initially hidden ...]