SOURCE

		<div class="container1">
			<div class="box1">左边固定1</div>
			<div class="box2"></div>
		</div>
		<div class="container2">
			<div class="box3">左边固定2</div>
			<div class="box4"></div>
		</div>

			.container1 {
				position: relative;
				top: 50px;
				margin: 0 20px;
				height: 300px;
			}
			.box1 {
				position: absolute;
				left: 0;
				width: 400px;
				height: 300px;
				background-color: #ED3E3E;
				line-height: 300px;
				font-size: 36px;
			}
			.box2 {
				position: absolute;
				top: 0;
				bottom: 0;
				left: 400px;
				right: 0;
				background-color: #43BC60;
			}
			.container2 {
				height: 300px;
				margin: 100px 20px;
			}
			.box3 {
				float: left;
				width: 400px;
				height: 300px;
				background-color: #a6c1ff;
				line-height: 300px;
				font-size: 36px;
			}
			.box4 {
				float: right;
				width: calc(100% - 400px);
				height: 300px;
				background-color: #FA7D3C;
			}