JSFiddle Link
CSS
.grid_1, .grid_2 {
margin-left : 1.00%;
margin-right : 1.00%;
margin-bottom : 15px !important;
float : left;
display : block;
-webkit-box-sizing: border-box;
/* Safari/Chrome, other WebKit */
-moz-box-sizing: border-box;
/* Firefox, other Gecko */
box-sizing: border-box;
/* Opera/IE 8+ */
}
.grid_1 {
width: 98%;
}
.grid_2 {
width: 48%;
}
.bg {
background-color:#ccc;
}
HTML:
<div class="grid_1 ">
<div class="grid_2">
<div class="grid_1 bg">1</div>
<div class="grid_1 bg">3<br> dgdgdfgdfg<br> sdrfsdrfrter</div>
<div class="grid_1 bg">5</div>
<div class="grid_1 bg">7</div>
<div class="grid_1 bg">9</div>
<div class="grid_1 bg">11</div>
</div>
<div class="grid_2">
<div class="grid_1 bg">2</div>
<div class="grid_1 bg">4</div>
<div class="grid_1 bg">6</div>
<div class="grid_1 bg">8</div>
<div class="grid_1 bg">10</div>
<div class="grid_1 bg">12</div>
</div>
</div>