<script type="text/javascript" src="http://code.jquery.com/jquery-1.4.3.min.js"></script>
<script type="text/javascript">
function getcookie(name){var aCookie = document.cookie.split(';');for(var i=0;i<aCookie.length;i++){while(aCookie[i][0]==' '){aCookie[i]=aCookie[i].substr(1);}var aCrumb=aCookie[i].split('=');if(name==aCrumb[0]){return unescape(aCrumb[1]);}}return null;}

function setcookie(name,value,expires,path,domain,secure){var today=new Date();var expires_date=new Date(today.getTime()+(expires*1000));document.cookie =name+'='+escape(value)+(expires ? ';expires='+expires_date.toUTCString():'')+(path ? ';path='+path:'')+(domain ? ';domain='+domain:'')+(secure ? ';secure':'')}

jQuery(function(){
$('.toggbutt').toggle(
function(){
         setcookie('display','none');
         $('#qwerty').css({display:getcookie('display')});
       },
       function(){
         setcookie('display','block');
         $('#qwerty').css({display:getcookie('display')});
       }
);
});
</script>
<input type="button" class="toggbutt" value="Спрятать / Показать" />
<div id="qwerty">qweqweqweqweqweqweqweqwe</div>