#container {
    display: flex;
    justify-content: center;
    margin: 0 auto; 
    flex-direction: column; /*上下排列*/
}

#header {
    display: flex;
    margin: 0 auto;
    flex-direction: column; /*上下排列*/
    border-bottom: 6px solid gainsboro;
}

#sidebar {
    width: 450px;
    text-align: left;
    overflow: hidden;
    border: 1px solid #FFFFFF;

}

#menu {
    display: flex;
    justify-content: end;/*紧贴右侧对齐*/
}

#footer {
    margin: 0 auto;
    margin-top: 10px;
    background-color: #0e3717;
    text-align: center; /*文本居中*/
    line-height: 60px;
    color: white;
    height: 60px; /*不设宽高无法判定背景颜色长宽*/
    width: 900px;
}

#pagebody {
    display: flex;
    margin: 0 auto;
    margin-top: 10px;
}

#mainbody img {
    width: 100%;
}

#menu {
    display: flex;
    flex-wrap: wrap;
    margin-top: -65px;
}

#banner {
    margin-top: 22px;
    bottom: 5px solid #000000;
    clear: both
}

a {
    text-decoration: none;/*取消下划线*/
    color: #6f6f6f;
    flex-direction: row; /*左右排列*/
}

a:hover {
    color: #FF0000
}

ul {
    list-style-type: none;/*取消原点*/
    flex-wrap: wrap;
    flex: 0 0 auto;
    display: flex;
    height: 150%;
    margin-right: 10px;

}

li {
    position: relative;/*绝对定位*/
    align-items: center;
    font-weight: 600;
    border: none;
    height: 150%;
    margin-right: 5px;

}

li a {
    display: flex;
    width: 100%;
    height: 150%;
}

li a::after { /*伪类*/
    content: ""; /*加上后才能用这个伪类*/
    border-right: gray solid 1px;
    margin-left: 10px;
}


li:nth-child(11) a::after { /*li元素的第11个a取消掉线*/
    border: none;
}