用flex做垂直居中

<div class="flex-cont flex-centerbox">
       <div class="center-cont">
            <h2>Title</h2>
            <p>infomation </p>
            <p>infomation </p>
            <button class="f-btn">btn</button>
       </div>
</div>

css

.flex-cont{
    /*定义为flexbox的"父元素"*/
    display: -webkit-box;
    display: -webkit-flex;
    display: flex;
}
.flex-item{
    /*给"子元素"赋予*伸缩的能力*/
    -webkit-box-flex:;
    -webkit-flex:;
    flex:;
    width: 0%;
}
/*垂直居中*/
.flex-centerbox{
    width: 100%;
    height: 200px;
    background: #fafafa;
    /*子元素沿主轴对齐方式居中*/
    -webkit-box-pack: center;
    -webkit-justify-content: center;
    justify-content: center;
    /*子元素沿侧轴对齐方式垂直居中*/
    -webkit-box-align: center;
    -webkit-align-items: center;
    align-items: center;
    border-top:1px solid #ddd;
    border-bottom: 1px solid #ddd;
    padding:10px 0;
    margin:10px 0;
}
.center-cont{
    display: block;
    background: #ddd;
    text-align: center;
    padding:20px;
    margin:10px;
}