You don't need the div's.
HTML:
<div class="nav3" style="height:705px;">
<a href="http://www.facebook.com/" class="icons"><img src="images/facebook.png"></a>
<a href="https://twitter.com" class="icons"><img src="images/twitter.png"></a>
</div>
CSS:
.nav3 {
background-color: #E9E8C7;
height: auto;
width: 150px;
float: left;
padding-left: 20px;
font-family: Arial, Helvetica, sans-serif;
font-size: 12px;
color: #333333;
padding-top: 20px;
padding-right: 20px;
}
.icons{
display:inline-block;
width: 64px;
height: 64px;
}
a.icons:hover {
background: #C93;
}
See this fiddle