css simple adaptation of the width of pages

1、css样式
.lgn{
width:500px;
height:20px;
}
.item_left_yd{
float: left;
display: inline-block;
width:240px ;
height: 100%;
}
.item_con li img{
width: 100%;
height: 140px;
}
.item_right_yd{
margin-left: 254px;
height: 100%;
background-color: #666666;
vertical-align: top;
}
2、html

<div class="lgn">
<div class="item_left_yd">
<img src="http://b-ssl.duitang.com/uploads/blog/201412/20/20141220101913_2XLSV.jpeg">
</div>
<div class="item_right_yd">
qwe
</div>
</div>