Hide/show header

[Dave Hawley]

Hi all

I currently have used "Header on/off" link to give users the ability to hide the header. I used some JavaScript and a Div found via a Google search. That is;

<a style="text-decoration: none" href="javascript:;" onmousedown="if(document.getElementById('tdiv').style.display == 'none'){ document.getElementById('tdiv').style.display = 'block'; }else{ document.getElementById('tdiv').style.display = 'none'; }"><span style="font-size: 6pt">
Header on/off</span></a> 
<a name="top"></a></p>

<div id="tdiv" style="width: 938; height: 200">

HEADER STUFF HERE

</div>

It works but ONLY until the user changes page on the forum, then it defaults back to show (on).

What I would like to do is retain the members choice until they either log out or close my forum in their browser.

Is there any hack out there, or anyone willing to share some code?