#gonggao { width: 1080px; height: 237px; position: absolute; left: 50%; margin-left: -595px; z-index: 1500; }#downloada { float: left; width: 1280px; height: 237px; overflow: hidden; margin-right: 200px; margin-top: -210px; }#downloada .btn_downa { float: left; width: 328px; height: 200px; position: relative; text-indent: -9999em; background: url("../images/fast_down1.png") left bottom no-repeat; display: block; margin-top: 10px; }#downloada .btn_downa:hover { text-decoration: none; background: url("../images/fast_down1_hover.png") left top no-repeat; }#downloada .btn_downb { float: left; width: 328px; height: 200px; position: relative; text-indent: -9999em; background: url("../images/fast_down2.png") left bottom no-repeat; display: block; margin-left: 100px; }#downloada .btn_downb:hover { text-decoration: none; background: url("../images/fast_down2_hover.png") left top no-repeat; }#downloada .btn_downc { float: left; width: 328px; height: 200px; position: relative; text-indent: -9999em; background: url("../images/fast_down3.png") left bottom no-repeat; display: block; margin-left: 100px; margin-top: 0px; }#downloada .btn_downc:hover { text-decoration: none; background: url("../images/fast_down3_hover.png") left top no-repeat; }