img position
background-position
.spico_all{background-image: url("http://news.pchome.com.tw/img/iconweather_SP.png")}
.wth_icon_am01{background-position: 0 0px}/*01晴天*/
.wth_icon_pm01{background-position: -50px 0px}/*01N晴天*/
.wth_icon_am02,.wth_icon_pm02{background-position: -100px 0px}/*02-02N多雲*/
.wth_icon_am03,.wth_icon_pm03{background-position: -150px 0px}/*03-03N陰天*/