From Math Images
Usage
{{HideShow|text to hide|number of chars to show}} or {{HideShow|1=text to hide|2=number of chars to show}}. The second form is required when "text to hide" contains an equals sign. This produces:
[Click to see more.]
text to hide
This is a title
And here is som
[...] [Click here to hide.]
text to hide
This is a title
And here is some more text below the title