var date = new Date();
var bg_date = date.getDate();

if(!localStorage.bg_img || localStorage.bg_date != bg_date)
{
    var bg_img_random = Math.round(Math.random()*8+1);
    localStorage.bg_img = bg_img_random + ".jpg";
    localStorage.bg_date = bg_date;
}
document.getElementById('body').style.background = "url('img/gradient_400px.png') top left repeat-x, url('img/bg/" + localStorage.bg_img + "') top left repeat";