function getCSS()
{
hour_bg = (new Date()).getHours();
if((hour_bg >=  0) && (hour_bg <  6))
display = "./css/bg_night.css";
else if((hour_bg >=  6) && (hour_bg < 18))
display = "./css/bg_noon.css";
else if((hour_bg >=  18) && (hour_bg < 24))
display = "./css/bg_night.css";
var css = '<'; css+='link rel="stylesheet" href=' + display + ' ?/'; css+='>';
document.write(css);
}