Anyone able to enlighten why would the links in the footer move when it is being moused over?

Any help rendered is greatly appreciated.

Link to website.

Code:
<!--footer start --> 
<div id="footer">
  <div id="footer-holder">
    <div class="footer-nav">
      <ul>
        <li><b><u>About Us</u></b></li>
        <li><a href="<?php echo $this->getUrl('aboutus') ?>">Clothing Republic</a></li>
        <li><a href="<?php echo $this->getUrl('customer/account/create') ?>">Sign up</a></li>
        <li><a href="<?php echo $this->getUrl('latest-update') ?>">Latest update</a></li>
        <li><a href="<?php echo $this->getUrl('terms-conditions') ?>">Terms and Conditions</a></li>
        <li><a href="<?php echo $this->getUrl('privacy-policy') ?>">Privacy Policy</a></li>
        <li><a href="<?php echo $this->getUrl('disclaimer') ?>">Disclaimer</a></li>
      </ul>
    </div>
    <div class="footer-nav">
      <ul>
        <li><b><u>Customer Services</u></b></li>
        <li><a href="<?php echo $this->getUrl('contacts') ?>">Contact us</a></li>
        <li><a href="<?php echo $this->getUrl('payment') ?>">Payment</a></li>
        <li><a href="<?php echo $this->getUrl('buying-guide') ?>">Buying guide</a></li>
        <li><a href="<?php echo $this->getUrl('shipping-delivery') ?>">Shipping and Delivery</a></li>
        <li><a href="<?php echo $this->getUrl('return-policies') ?>">Return Policies</a></li>
      </ul>
    </div>
    <div class="footer-nav">
      <ul>
        <li><b><u>Payment Methods</u></b></li>
        <li><img src="<?php echo $this->getSkinUrl('image/Payment_Method_Logo.png'); ?>" alt="" title="" border="0"/></li>
      </ul>
    </div>
    <div class="footer-nav">
      <ul>
        <li><b><u>Shipping Methods</u></b></li>
        <li><a href="http://www.singpost.com/" target="_blank"><img src="<?php echo $this->getSkinUrl('image/Singpost.png'); ?>" alt="" title="" border="0"/></a></li>
        <li><a href="http://www.citylinkexpress.com/main.php" target="_blank"><img src="<?php echo $this->getSkinUrl('image/Citylink.png'); ?>" alt="" title="" border="0"/></a></li>
        <li><a href="http://www.ups.com" target="_blank"><img src="<?php echo $this->getSkinUrl('image/UPS1.png'); ?>" alt="" title="" border="0"/></a></li>
      </ul>
    </div>
    <div class="footer-nav">
      <ul>
        <li><b><u>Follow Us On</u></b></li>        
        <div style="padding-left:1px;"><a href="https://www.facebook.com/pages/Clothing-Republic/245763695465304" target="_blank" title=""><img src="<?php echo $this->getSkinUrl('image/fb.png'); ?>" alt="" title="" border="0"/></a>
        <a href="https://plus.google.com/b/114348134915957682266/114348134915957682266/posts" target="_blank" title=""><img src="<?php echo $this->getSkinUrl('image/Google.png'); ?>" alt="" title="" border="0"/></a>
        <a href="https://twitter.com/@republiclothing" target="_blank" title="Follow us on Twitter"><img src="<?php echo $this->getSkinUrl('image/twitter.png'); ?>" alt="" title="" border="0"/></a>
        <a href="https://pinterest.com/republiclothing/" target="_blank" title="Follow us on Pinterest"><img src="<?php echo $this->getSkinUrl('image/Pinterest.png'); ?>" alt="" title="" border="0" /></a></div>
      </ul>
        </div>
    </div>
  	
  <div id="credit">
    <table cellpadding="0" cellspacing="0">
      <tr>
        <td><?php echo $this->getCopyright() ?></td>
        <td><img src="<?php echo $this->getSkinUrl('image/bg-sign.png'); ?>" alt="" title="" border="0"/></td>
      </tr>
    </table>
  </div>
</div>
</div>
<!--footer end -->
CSS
Code:
#footer {
	background:url(../image/bg-footer.png) top left no-repeat;
	width:960px;
	height:260px;
}
#footer-holder {
	height:200px;
	width:880px;
	overflow:hidden;
	padding: 20px 50px 0;
}
.footer-nav {
	float:left;
	width:155px;
	margin:0 20px 0 0;
}
.footer-nav ul li {
	display:block;
	color:#ffffff;
	padding:2px 5px;
	text-transform:uppercase;
	/*font-family: Tahoma, Geneva, sans-serif;*/
        font-family: Candara, Arial;
        font-size:12px;
	font-weight:bold;
}
.footer-nav ul li a.email {
	
	text-decoration:none;
	color:#ffffff;
	text-transform:uppercase;
	/*font-family: Tahoma, Geneva, sans-serif;*/
        font-family: Candara, Arial;
	font-size:12px;
	font-weight:normal;
	padding:0;
	background:none;
}
.footer-nav ul li a.email:hover {
	display:block;
	text-decoration:underline;
	color:#ffffff;
	text-transform:uppercase;
	/*font-family: Tahoma, Geneva, sans-serif;*/
        font-family: Candara, Arial;
	font-size:12px;
	font-weight:normal;
	padding:0;
	background:none;
}
.footer-nav ul li a {
	display:block;
	text-decoration:none;
	color:#ffffff;
	padding:0px 0px;
	text-transform:uppercase;
	/*font-family: Tahoma, Geneva, sans-serif;*/
        font-family: Candara, Arial;
	font-size:12px;
	font-weight:normal;
	/*background:url(../image/arrow-white.png) left no-repeat;*/
}
.footer-nav ul li a:hover {
	display:block;
	text-decoration:underline;
	color:#ffffff;
	padding:2px 0px;
	text-transform:uppercase;
	/*font-family: Tahoma, Geneva, sans-serif;*/
        font-family: Candara, Arial;
	font-size:12px;
	font-weight:normal;
	/*background:url(../image/arrow-white.png) left no-repeat;*/
}
#credit {
	width:600px;
	margin:0 auto;
	text-align:center;
	/*font-family: Tahoma, Geneva, sans-serif;*/
        font-family: Candara, Arial;
	font-size:10px;
	color:#666666;
	text-transform:uppercase;
}