Create cells and float them.
HTML:
<div id="container">
<div id="cell1">
<div>Article1</div>
<div>Article2</div>
</div>
<div id="cell2">
<div>Article3</div>
<div>Article4</div>
</div>
<div id="cell3">3</div>
</div>
CSS:
#container{
width: 100%;
overflow: hidden;
}
#cell1{
float: left;
width: 33%;
background-color:red;
}
#cell2{
float: left;
width: 33%;
background-color:blue;
}
#cell3{
float: left;
width: 33%;
background-color:green;
}