相关代码：

header, footer {
    width: 100%;
    height: 50px;
}
header {
    background-color: red;
    display: -webkit-box;
    display: -webkit-flex;
    display: -moz-box;
    display: -ms-flexbox;
    display: flex;
}
footer {
    background-color: green;
}

.flexbox header {
    display: -webkit-box;
    display: -webkit-flex;
    display: -moz-box;
    display: -ms-flexbox;
    display: flex;
    -webkit-box-pack: center;
    -webkit-justify-content: center;
       -moz-box-pack: center;
        -ms-flex-pack: center;
            justify-content: center;
    -webkit-box-align: center;
    -webkit-align-items: center;
       -moz-box-align: center;
        -ms-flex-align: center;
            align-items: center;
}
.no-flexbox header {
    text-align: center;
    line-height: 50px;
}

​