双飞翼布局

• html

    

        

            

                中间自适应
            
        
        

            
I'am left
        
        

            
I'am right
        
    

• css

*{
    padding: 0;
    margin: 0;
}
.content{
    box-sizing: border-box;
    width: 100%;
}
.main{
    width: 100%;
    float: left;
}
.main_content{
    background: #f66;
    margin: 0 200px;
    height: 100px;
}
.left{
    background:#fcc;
    width: 200px;
    float: left;
    margin-left: -100%;
    height: 50px;
}
.right{
    background: #fcc;
    width: 200px;
    float: left;
    margin-left: -200px;
    height: 60px;
}