<div class="header">
    <span class="line"></span>
    <span class="text">中间文字，两边横线</span>
    <span class="line"></span>
</div>

<style>
.header
{
    width:400px;
    height:36px;
    line-height:36px;
    border:1px solid green;
    text-align:center;
}
.line
{
    display:inline-block;
    width:100px;
    border-top:1px solid #cccccc;
    vertical-align:5px;  
　　//看到网上有把.text设置为vertical-align:-5px的，试了一下感觉和.header设置的line-height有冲突,效果不太合适。所以将vertical-align设置到.line上了
}
</style>

<div class="header">
    <div>中间文字,两边横线</div>
</div>

<style>
    .header
    {
        width:400px;
        height:36px;
        line-height: 36px;
        text-align:center;
        border:1px solid green;
        position:relative;
    }
    .header div:before,.header div:after
    {
        position:absolute;
        background:#ccc;
        content:"";
        height:1px;
        top:50%;
        width:100px;
    }
    .header div:before{left:10px;}
    .header div:after{right:10px;}
</style>