.main,.sitebar{

      height: 300px;

      font: bolder 20px/300px "微软雅黑";

      color: black;

      text-align: center;

}

.main{

      width: 100%;

      float: left;

}

.main .content{

      margin-left: 200px;

      background: red;

}

.sitebar{

      width: 200px;

      float: left;

      margin-left: -100%;

      background: green;

}

<

div

class

=

"main"

>

      <

div

class

=

"content"

>

hhhhhhhhhhhhh

</

div

>

</

div

>

<

div

class

=

"sitebar"

>

      hehhehhe

</

div

>