U.Helper

function setCookie(name, value, days) {
   if (days) {
    var date = new Date();
    date.setTime(date.getTime() + (days * 24 * 60 * 60 * 1000));
    var expires = "; expires=" + date.toGMTString();
   }
   else var expires = "";
   document.cookie = name + "=" + value + expires + "; path=/";
}
     
function getCookie(name) {
   var nameEQ = name + "=";
   var ca = document.cookie.split(';');
   for (var i = 0; i < ca.length; i++) {
    var c = ca[i];
    while (c.charAt(0) == ' ') c = c.substring(1, c.length);
    if (c.indexOf(nameEQ) == 0) return c.substring(nameEQ.length, c.length);
   }
   return null;
}
     
function eraseCookie(name) {
   setCookie(name, "", -1);
}
     
function expandCollapse(id) {
   var div = document.getElementById(id.split(':')[0]);
   var status = div.style.display == 'none' ? 'block' : 'none';
   div.style.display = status;
   if (getCookie('informers')) {
    eraseCookie('informers');
    setCookie('informers', status, 30);
   } else {
    setCookie('informers', status, 30);
   }
     
     
}
     
function initInformers(id) {
   if (getCookie('informers')) {
    document.getElementById(id.split(':')[0]).style.display = getCookie('informers');   
   }
}
     
function random_img()
{
       var src = arguments[Math.floor(Math.random() * arguments.length)];
       document.write("<img src=\"" + src + "\"/>");
}

<div id="blockНОМЕР_БЛОКА" style="display:block;"><script type="text/javascript">initInformers('blockНОМЕР_БЛОКА');</script>

</div>

onClick="expandCollapse('blockНОМЕР_БЛОКА');"