Hidden DIV problem..?

How can I show hidden div in the editor ?
For ex.

<div id="z2" style="display:none">

Edit me Edit me Edit me Edit me Edit me Edit me Edit me Edit me Edit me

</div>

If I click source button I can see but lot of people dont understant html code and format
If its possible I want a button "show hidden layers" or some think like that..

Can some one help me ?

Thanx