块级元素居中

方式一： 利用margin
<! DOCTYPE  html>
< html >
    < head >
        < title >块级元素水平，垂直居中</ title >
        < meta  charset="utf-8">
        < style >
            .wrapper {
                height: 600px;
                border: 1px solid gray;
            }
            .box {
                width: 100px;
                height: 100px;
                background: gold;
                margin: 250px auto 0;
            }
        </ style >
    </ head >
    < body >

        < div  class="wrapper">
            < div  class="box"></ div >
        </ div >
    </ body >
</ html >


方式二，利用定位及负边距

<! DOCTYPE  html>
< html >
    < head >
        < title >块级元素水平，垂直居中</ title >
        < meta  charset="utf-8">
        < style >
            .wrapper {
                height: 600px;
                border: 1px solid gray;
                position: relative;
            }
            .box {
                width: 100px;
                height: 100px;
                background: gold;
                position: absolute;
                left: 50%;
                top: 50%;
                margin-left: -50px;
                margin-top: -50px;
            }
        </ style >
    </ head >
    < body >
        < div  class="wrapper">
            < div  class="box"></ div >
        </ div >
    </ body >
</ html >