设置最低高度为100%

html{
    padding:0;
    margin:0;
    height:100%;
}
body{
    padding:0;
    margin:0;
    font-family: "Microsoft YaHei","Helvetica Neue",Helvetica,Roboto,Arial,sans-serif;
    background-color:#f0f0f0;
    height:100%;
}
.wrap{
    height:auto;
    min-height:100%;
    _height:100%;
}
.main{
    padding-bottom:76px;
}
.footer{
    text-align:center;
    background:#27303f;
    color:#fff;
    height:76px;
    font-size: 14px;
    margin-top:-76px;
}