SOURCE

<div class="parent">
	<div class="left">
		<p>左侧定宽</p>
	</div>
	<div class="right">
		<p> 右侧定宽</p>
	</div>
	<div class="center">
		<p>中间自适应</p>
	</div>
</div>

.parent {
    height: 75px;
    font-size: 14px;
    color: #fff8f8;
}

.left {
    float: left;
    width: 100px;
    height: 100%;
    margin-right: 10px;
    background-color: #77a4ff;
}

.center {
    height: 100%;
    overflow: hidden;
    background-color: #ff926d;
}

.right {
    float: right;
    width: 100px;
    height: 100%;
    margin-left: 10px;
    background-color: #ae92fa;
}