style_from_cookie()
{
  var css_title = get_cookie( style_cookie_name );
  if (css_title.length) {
    switch_style( css_title );
  }
}
function set_cookie ( cookie_name, cookie_value,
    lifespan_in_days, valid_domain )
{
    // http://www.thesitewizard.com/javascripts/cookies.shtml
    var domain_string = valid_domain ?
                       ("; domain=" + valid_domain) : '' ;
    document.cookie = cookie_name +
                       "=" + encodeURIComponent( cookie_value ) +
                       "; 