function GetCookie(NameOfCookie)
{
    // First we check to see if there is a cookie stored.
    // Otherwise the length of document.cookie would be zero.
    if (document.cookie.length > 0)
    {
        // Second we check to see if the cookie's name is stored in the
        // "document.cookie" object for the page.
        
        // Since more than one cookie can be set on a
        // single page it is possible that our cookie
        // is not present, even though the "document.cookie" object
        // is not just an empty text.
        // If our cookie name is not present the value -1 is stored
        // in the variable called "begin".

        begin = document.cookie.indexOf(NameOfCookie+"="); 
        if (begin != -1) // Note: != means "is not equal to"
        {
            // Our cookie was set. 
            // The value stored in the cookie is returned from the function.
            begin += NameOfCookie.length+1; 
            end = document.cookie.indexOf(";", begin);
            if(end == -1) end = document.cookie.length;
            return unescape(document.cookie.substring(begin, end));
        }
    }
    
    // Our cookie was not set. 
    // The value "null" is returned from the function.
    return null;
}

function SetCookie(NameOfCookie, value, expiredays) 
{
    // Three variables are used to set the new cookie. 
    // The name of the cookie, the value to be stored,
    // and finally the number of days until the cookie expires.
    // The first lines in the function convert 
    // the number of days to a valid date.
    var ExpireDate = new Date ();
    ExpireDate.setTime(ExpireDate.getTime() + (expiredays * 24 * 3600 * 1000));

    // The next line stores the cookie, simply by assigning 
    // the values to the "document.cookie" object.
    // Note the date is converted to Greenwich Mean time using
    // the "toGMTstring()" function.
    document.cookie = NameOfCookie + "=" + escape(value) + 
                      ((expiredays == null) ? "" : "; expires=" + ExpireDate.toGMTString());
}

function DeleteCookie(NameOfCookie) 
{
    // The function simply checks to see if the cookie is set.
    // If so, the expiration date is set to Jan. 1st 1970.
    if (GetCookie(NameOfCookie))
    {
        document.cookie = NameOfCookie + "=" +
                          "; expires=Thu, 01-Jan-70 00:00:01 GMT";
    }
}