HTML部分

<!-- 登录弹窗 -->
<div id="login">
    <div class="mask"></div>
    <div class="content">
        <span><i class="shutdown" ></i></span>
        <form action="">
            <p>登录网易云课堂</p>
            <p><input class="id" type="text"  placeholder="帐号"></p>
            <p><input class="pw" type="text"  placeholder="密码"></p>
            <p><input class="btn" type="button" value="登录" ></p>
        </form>
    </div>
</div>

CSS部分

/* 登录弹窗 */
#login{
    height: 100%;
    width: 100%;
}
#login .mask{
    height: 100%;
    width: 100%;
    position: fixed;
    top: 0;z-index: 1000;
}
#login .mask{
        background-color: #000;
        opacity: 0.5;
}
#login .content{
    width: 387px;
    height: 298px;
    position: fixed;
    top: 50%;
    left: 50%;
    transform: translate(-50%,-50%);
    z-index: 1001;
    background-color: #fff;
    box-sizing: border-box;
    padding: 30px 53px 18px 38px;
}
#login .content .shutdown{
    position: absolute;
    top: 10px;
    right: 9px;
}
#login .content p{
    font: 18px/28px 微软雅黑;
    color: #444444;
    font-weight: 600;
}
#login .content .shutdown{
    display: inline-block;
    background: #fff url(../images/icon.jpg)  no-repeat -16px 0;
    width: 10px;
    height: 12px;
    padding-right: 6px;
    overflow: hidden;
    vertical-align: text-bottom;
    cursor: pointer;
}
#login .content .id{
    margin-top: 20px;
}
#login .content input{
    width: 295px;
    height: 45px;
    margin-bottom: 15px;
    border: 1px solid #dfdfdf;
    padding-top: 5px;
    padding-left: 10px;
    font: 18px/28px 微软雅黑;
    color: #ccc;
    background: #fafafa;
}
#login .content .btn{
    margin-top: 13px;
    margin-bottom: 10px;
    background: #2db352;
    font-size: 16px;
    color: #fff;
}

效果预览

弹窗.jpg