[рони]

Quark_,

var limit = 24 * 3600 * 1000; // 24 часа
var localStorageInitTime = localStorage.getItem('localStorageInitTime') || new Date();
var delta = new Date() - localStorageInitTime;
if(delta > limit) localStorage.removeItem('hide');
var idPC = document.getElementById('ppp_close');
var idPB = document.getElementById('ppp');

if(localStorage.getItem('hide') == 'none') {
    idPB.style.display = 'none';
}

function onclickPC() {
    idPB.style.display = 'none';
    localStorage.setItem('hide', 'none');
    localStorage.setItem('localStorageInitTime', +new Date());
}