Hi. I recently discovered that my website has some W3 validation errors that I do not understand. I hope that some of you will be able to shed some light on these errors. I got many errors (up to 72 errors on a page) and they are basically the same throughout the website. Below I have copied the code and the validation errors I get. I have removed a lot of text to shorten it down.

Here is my code

<body>

<div class="container">
<div class="header">
<p><br class="clearfloat" />
</p>
<p>&nbsp;</p>
<p>&nbsp;</p>
<p>&nbsp;</p>
<p>&nbsp;</p>
<div id="navMenuWrapper">

<div id="navMenu">

<ul>

<li> <a href="index.html">Home</a> <!-- Hovedpunkt -->
</li>
<!-- end main LI -->
</ul> <!-- end main UL -->

<ul>

<li> <a href="#">About nightvision</a> <!-- Hovedpunkt -->

<ul>

<li><a href="what_is_night_vision.html">what is night vision</a></li>
<br /> <!-- Underpunkt -->
<li><a href="uses_of_nightvision.html">Uses of Night Vision</a></li>
<br /> <!-- Underpunkt -->
<li><a href="all_our_night_vision_videos.html">Night Vision Videos</a></li>
<br /> <!-- Underpunkt -->

</ul> <!-- end inner UL -->

</li> <!-- end main LI -->

</ul> <!-- end main UL -->

<ul>

<li> <a href="#">Products</a> <!-- Hovedpunkt -->

<ul>

<li><a href="night_vision_for_home_use.html">Night Vision for home use</a></li>
<br /> <!-- Underpunkt -->
<li><a href="night_vision_for_professionals.html">Night Vision for professionals</a></li>
<br /> <!-- Underpunkt -->
<li><a href="night_vision_for_hunting.html">Night Vision for hunting</a></li>
<br /> <!-- Underpunkt -->
<li><a href="night_vision_for_recreational_use.html">Night Vision for recreation</a></li>
<br /> <!-- Underpunkt -->
<li><a href="thermal_imaging.html">Thermal Imaging</a></li>
<br /> <!-- Underpunkt -->
<li><a href="Accessories_for_night_vision.html">Accessories for Night Vision</a></li>
<br /> <!-- Underpunkt -->
<li><a href="All_Nightvision_products.html">All Night Vision products</a></li>
<br /> <!-- Underpunkt -->
<li><a href="price_guarantee.html">Price guarantee</a></li>
<br /> <!-- Underpunkt -->
<li><a href="rent.html">Rent a device</a></li>
<br /> <!-- Underpunkt -->
<li><a href="Additional_Products.html">Additional products</a></li>
<br /> <!-- Underpunkt -->

</ul> <!-- end inner UL -->

</li> <!-- end main LI -->

</ul> <!-- end main UL -->

<ul>

<li> <a href="shipping_and_return.html">Shipping</a> <!-- Hovedpunkt -->
</li>
<!-- end main LI -->

</ul> <!-- end main UL -->

<ul>

<li> <a href="special_deals.html">Special deals</a> <!-- Hovedpunkt -->
</li>
<!-- end main LI -->

</ul> <!-- end main UL -->

<ul>

<li> <li> <a href="#">About us</a> <!-- Hovedpunkt -->
<ul>

<li><a href="About_Us.html">Who we are</a></li>
<br /> <!-- Underpunkt -->
<li><a href="about_our_website.html">About our website</a></li>
<br /> <!-- Underpunkt -->
<li><a href="get_our_newsletter.html">Get our newsletter</a></li>
<br /> <!-- Underpunkt -->

</ul> <!-- end inner UL -->
</li>
<!-- end main LI -->

</ul> <!-- end main UL -->

<ul>

<li> <a href="contact_us.html">Contact us</a> <!-- Hovedpunkt -->
</li>
<!-- end main LI -->

</ul> <!-- end main UL -->


<ul>

<li> <a href="faq.html">FAQ</a> <!-- Hovedpunkt -->
</li>
<!-- end main LI -->

</ul> <!-- end main UL -->


<ul>

<li> <a href="become_a_dealer.html">Dealer info</a> <!-- Hovedpunkt -->
</li>
<!-- end main LI -->
</ul>
<!-- end main UL -->



<br class="clearFloat" />

</div> <!-- end navMenu -->

</div> <!-- end navMenuWrapper -->
<!-- end .header --></div>


<br class="clearfloat" />

<!-- end .content --></div>
<div class="footer">
<table width="100%" border="0" cellspacing="0" cellpadding="0">
<tr>
<td width="6%" height="38" valign="top"><div class="g-plusone" data-size="medium"></div>
<script type="text/javascript">
(function() {
var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true;
po.src = 'https://apis.google.com/js/plusone.js';
var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s);
})();
</script>
&nbsp;&nbsp;</td>
<td width="9%"><div align="center"><a href="https://twitter.com/share" class="twitter-share-button style6" data-url="http://www.goblinnightvision.com">Tweet</a>
<script>!function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs");</script>
&nbsp;</div></td>
<td width="13%" valign="top"><iframe src="//www.facebook.com/plugins/like.php?href=http%3A%2F%2Fwww.goblinnightvision.com&amp;send=false&amp;layout=button_count&amp;widt h=450&amp;show_faces=true&amp;action=like&amp;colorscheme=light&amp;font=verdana&amp;height=21" scrolling="No" frameborder="0" style="border:none; overflow:hidden; width:110px; height:21px;" allowtransparency="true"></iframe></td>
<td width="41%" valign="top"><div align="right"><a href="warranty.html"><span class="style13">Warranty</span></a></div></td>
<td width="1%" valign="top">&nbsp;</td>
<td width="14%" valign="top"><div align="right"><a href="what_is_night_vision.html"><span class="style13">What Is Night Vision</span></a></div></td>
<td width="1%" valign="top">&nbsp;</td>
<td width="7%" valign="top"><div align="right"><a href="get_our_newsletter.html"><span class="style13">Newsletter</span></a></div></td>
<td width="1%" valign="top">&nbsp;</td>
<td width="5%" valign="top"><div align="right"><a href="sitemap.html"><span class="style13">Sitemap</span></a></div></td>
</tr>
</table>
<p align="center"><a id="bbblink" class="sehzbum" href="http://www.bbb.org/lexington/business-reviews/night-vision-equipment/goblin-nightvision-in-lexington-ky-9107293#bbblogo" title="Goblin NightVision, Night Vision Equipment, Lexington, KY" style="display: block;position: relative;overflow: hidden; width: 150px; height: 57px; margin: 0px; padding: 0px;"><img style="padding: 0px; border: none;" id="bbblinkimg" src="http://seal-bluegrass.bbb.org/logo/sehzbum/goblin-nightvision-9107293.png" width="300" height="57" alt="Goblin NightVision, Night Vision Equipment, Lexington, KY" /></a><script type="text/javascript">var bbbprotocol = ( ("https:" == document.location.protocol) ? "https://" : "http://" ); document.write(unescape("%3Cscript src='" + bbbprotocol + 'seal-bluegrass.bbb.org' + unescape('%2Flogo%2Fgoblin-nightvision-9107293.js') + "' type='text/javascript'%3E%3C/script%3E"));</script>
<!-- end .footer --></div>
<!-- end .container --></div>

<map name="Map" id="Map"><area shape="rect" coords="2,1,117,131" href="#" /></map>
<map name="Map2" id="Map2"><area shape="rect" coords="2,1,385,291" href="#" /></map>
<script type="text/javascript" src="js/default.js"></script></body>

Here is the validation errors

Validation Output: 72 Errors

Line 60, Column 13: document type does not allow element "br" here; assuming missing "li" start-tag
<br /> <!-- Underpunkt -->

Line 61, Column 11: document type does not allow element "li" here; missing one of "ul", "ol", "menu", "dir" start-tag
<li><a href="uses_of_nightvision.html">Uses of Night Vision</a></li>


Line 66, Column 12: end tag for "li" omitted, but OMITTAG NO was specified
</ul> <!-- end inner UL -->


Line 60, Column 8: start tag was here
<br /> <!-- Underpunkt -->


Line 137, Column 9: end tag for "li" omitted, but OMITTAG NO was specified
</ul> <!-- end main UL -->


Line 123, Column 6: start tag was here
<li> <li> <a href="#">About us</a> <!-- Hovedpunkt -->


Line 304, Column 28: end tag for "p" omitted, but OMITTAG NO was specified
<!-- end .footer --></div>