function RandomBG() {
    var bgs = new Array(4);
    bgs[0] = "bg1";
    bgs[1] = "bg2";
    bgs[2] = "bg3";
    bgs[3] = "bg4";
    var randomNumber;

    if (readCookie('bgCookie') == null) {
        //alert('no cookie');
        randomNumber = Math.floor(Math.random() * 4);
        createCookie('bgCookie', randomNumber, '');
    }
    else {
        //alert('cookie found : ' + readCookie('bgCookie'));
        randomNumber = readCookie('bgCookie');
    }
    $('#page').removeClass(bgs[randomNumber]);
    $('#page').addClass(bgs[randomNumber]);
}

function createCookie(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 readCookie(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) {
    createCookie(name, "", -1);
}


$(function() {
    //eraseCookie('bgCookie');
    RandomBG();
});