I have developed a website using Microsoft Expression Web 3. Please look at it www.homesfromtheheart.org

Everything seems to work nicely in the latest browser versions like IE8, Firefox, and Chrome. However, when the website is viewed on IE7 the horizontal navigation bar below the mast head is rendered as a vertical list of buttons which appear on top of page content. Additionally, all of the hotlinks within the body of every page are inactive on IE7. Any help would be greatly appreciated. Below is the relevant code, let me know if more information is needed. Thanks

<style type="text/css">

.Nav {
margin-top: 0;
margin-bottom: 0;
font-family: Arial, Helvetica, sans-serif;
text-align: center;
}
ol {
padding: 0px;
margin: 0px;
list-style-type: none;
width: auto;
display: inline-block;
float: left;
position: static;
}
ol ol {
float: inherit;
position: absolute;
left: auto;
display: none;
}
ol li {
position: relative;
display: inline-block;
z-index: 3;
}
li a {
margin: 0px 0px 1px 1px;
border-style: double none double none;
border-width: 2px;
border-color: #9C1109;
display: inline-block;
padding: 1px 1px 7px 3px;
background-color: #88b3db;
height: 10px;
width: 106px;
text-decoration: none;
color: #000000;
font-size: small;
font-family: Arial, Helvetica, sans-serif;
bottom: 0px;
top: 0px;
z-index: 3;
position: relative;
}

li:hover ol, li.over ol {
display: block;
}
#Header-Nav {
padding: 0px;
margin: 0px auto 0px auto;
width: 980px;
position: relative;
height: 199px;
z-index: 5;
}



<div id="Header-Nav">
<div id="Header"><img alt="" height="156" src="images/header.png" width="980" /></div>
<div id="spacer"></div>
<div id="Navigation">
<ol>
<li><a href="index.html">Home</a></li>
<li><a href="background.html">About Us</a>
<ol>
<li><a href="background.html">Background</a></li>
<li><a href="staff.html">Staff</a></li>
</ol>
</li>

<li><a href="sanluistalpa.html">Projects</a>
<ol>
<li><a href="sanluistalpa.html">San Luis Talpa</a></li>
<li><a href="soyapango.html">Soyapango</a></li>
</ol></li>
<li><a href="community.html">Community</a></li>
<li><a href="media.html" target="_blank">Media</a></li>
<li><a href="http://www.fullercenter.org">Partners</a><ol>
<li><a href="http://www.fullercenter.org">Fuller Center</a></li>
<li><a href="corp-ngo.html">Organizations</a></li>
<li><a href="universities.html">Schools</a></li>
<li><a href="churches.html">Churches</a></li>
</ol></li>
<li><a href="contact.html">Contact Us</a>
</li>
</ol>
</div>
<div id="feet"><img src="images/feet.gif" alt="feet" /></div>
</div>