常用布局的实现（两列布局、三列适应布局，两列等高适应布局等）

<style>
  * {
	margin: 0;
	padding: 0;
}

.main,.sitebar {
	font: bolder 20px/300px;
}

.main {
	width: 100%;
	float: left;
}

.main .content {
	margin-left: 200px;
	background-color: red;
}

.sitebar {
	width: 200px;
	float: left;
	background-color: green;
	margin-left: -100%;
}
  </style>
<div class="main"> 
   <div class="content">
     右侧主体自适应区块 
   </div> 
  </div> 
  <div class="sitebar">
    左侧定宽200px区块 
</div>

<style>       
 * {
	margin: 0;
	padding: 0;
}

.sitebar {
	float: left;
	width: 200px;
	background-color: green;
}

.content {
	background-color: red;
	margin-left: 200px;
}   
 </style>
<div class="sitebar">
   左侧定宽200px区块
  </div> 
  <div class="content">
   右侧主体自适应区块
</div>

<style>        
* {
	margin: 0;
	padding: 0;
}

.sitebar {
	width: 200px;
	background-color: green;
}

.content {
	position: absolute;
	left: 200px;
	right: 0;
	top: 0;
	background-color: red;
}   
 </style>
<div class="content">
   右侧主体自适应区块
  </div> 
  <div class="sitebar">
   左侧定宽200px区块
</div>

<style>        
* {
	margin: 0;
	padding: 0;
}

.main {
	display: flex;
}

.content {
	flex: 1;
	background-color: red;
}

.sitebar {
	flex: 0 0 200px;
	order: -1;
	background-color: green;
}            
</style>
<div class="main"> 
   <div class="content">
    右侧主体自适应区块
   </div> 
   <div class="sitebar">
    左侧定宽200px区块
</div>

<style>        
* {
	margin: 0;
	padding: 0;
}

.main,.left,.right {
	height: 300px;
	font: 20px/300px;
	color: #fff;
	text-align: center;
}

.main {
	width: 100%;
	float: left;
}

.main .content {
	margin: 0 300px 0 200px;
	background-color: black;
}

.left {
	width: 200px;
	float: left;
	margin-left: -100%;
	background-color: red;
}

.right {
	width: 300px;
	float: left;
	margin-left: -300px;
	background-color: blue;
}  
</style>
<div class="main"> 
   <div class="content">
    中间主体区域宽度自适应
   </div> 
  </div> 
  <div class="left">
   左侧定宽200px
  </div> 
  <div class="right">
   右侧定宽300px
</div>

<style>
body {
	margin: 0px;
}
#left {
	background-color: #E8F5FE;
	border: 1px solid #A9C9E2;
	height: 400px;
	width: 100px;
	position: absolute;
	top: 0px;
	left: 0px;
}

#center {
	background-color: #F2FDDB;
	border: 1px solid #A5CF3D;
	height: 400px;
	margin-right: 102px;
	margin-left: 102px;
}

#right {
	background-color: #FFE7F4;
	border: 1px solid #F9B3D5;
	height: 400px;
	width: 100px;
	position: absolute;
	top: 0px;
	right: 0px;
}
</style>
 <div id="center">
   中列
  </div> 
  <div id="left">
   左列
  </div> 
  <div id="right">
   右列
  </div>

<style>
.HolyGrail-body {
	display: flex;
	flex: 1;
}

.HolyGrail-content {
	flex: 1;
	background-color: green;
}

.HolyGrail-nav, .HolyGrail-ads {
  /* 两个边栏的宽度设为12em */
	flex: 0 0 200px;
	background-color: blue;
}

.HolyGrail-nav {
  /* 导航放到最左边 */
	order: -1;
	background-color: grey;
}
</style>
<div class="HolyGrail-body"> 
   <main class="HolyGrail-content">
    ...
   </main> 
   <nav class="HolyGrail-nav">
    ...
   </nav> 
   <aside class="HolyGrail-ads">
    ...
   </aside> 
  </div>