Just wanna update this for beginners now you should definitly use flexbox to do that, it's more appropriate and work for responsive try this : http://jsfiddle.net/x5vyC/3957/
#wrapper{
display:flex;
justify-content:space-between;
background:red;
}
#c1{
background:blue;
}
#c2{
background:green;
}
<div id="wrapper">
<div id="c1">con1</div>
<div id="c2">con2</div>
</div>?