案例

实现下图效果：

html

<div class="wrapper">
    <div class="shop_box">
        <div class="shop_box_w">
            <span class="car"></span>
            <span class="shop_num">100</span>
            <a href="#">我的购物车</a>
        </div>
        <div class="shop_menu"></div>
    </div>
</div>

css

.wrapper{
    width: 500px;
    font-size: 12px;
}
.shop_box{ 
    width: 132px;
    height: 36px;
    line-height: 36px;
    border: 1px solid transparent;
    position: relative;
    float: right;
}
.shop_box a{
    color: #e1251b;
    text-decoration: none;
}
.shop_num{
    background-color: #e1251b;
    color: #fff;
    min-width: 12px; /* 最小宽度,会根据内容调整宽度 */
    display: inline-block;
    padding: 1px 3px;
    border-radius: 7px;
    line-height: 12px;
    font-size: 12px;
    text-align: center;
    position: relative;
    top: -8px;
    left: -5px;
}
/* 鼠标放到购物车的边框 */
.shop_box:hover{
    border: 1px solid #c81623;
    /* border-bottom: 1px solid #fff; */
    border-bottom-color: transparent;
}
.shop_menu{
    width: 310px;
    height: 71px;
    background-color: #fff;
    position: absolute;
    display: none;
    border: 1px solid #c81623;
    top:35px;
    right: -1px;
}
.shop_box:hover .shop_menu{
    display: block;
}
.shop_box_w{
    background-color: #fff;
    position: relative;
    /* 在上面 */
    z-index: 99;
}
.car{
    width: 16px;
    height: 36px;
    display: inline-block;
    background-image: url(img/car.png);
    background-size: 16px 16px;
    background-repeat: no-repeat;
    background-position: 0 10px;
    float: left;
    margin-left: 15px;
}