.clearfix::after {
    clear: both;
    content: ".";
    display: block;
    height: 0;
    visibility: hidden;
}
.clearfix {
}
/* 必要布局样式css */
.sign-content {
    width: 780px;
    overflow: hidden;
    padding-top: 4px;
    padding-bottom: 1px;
}
.sign-nav {
    width: 780px;
    height: 39px;
    border-bottom: 2px solid #f1f1f1;
    line-height: 39px;
}
.sign-nav ul {
    width: 780px;
    float: left;
}
.sign-nav ul li {
    float: left;
    color: #4b4b4b;
    padding: 0px 20px;
    font-size: 15px;
    cursor: pointer;
    line-height: 38px;
    font-weight: bolder;
    font-size: 17px;
}
.sign-nav ul .on {
    border-left: 1px solid #f1f1f1;
    border-right: 1px solid #f1f1f1;
    border-top: 3px solid #cc0000;
    background: #fff;
    color: #000000;
    height: 41px;
    margin-top: -3px;
}