<ul class="mainMenu">
<li><a href="#">Home</a></li>
<li><a href="#">Forum</a></li>
<li><a href="#" class="mainSelected">Construct</a></li>
<li><a href="#">Arcade</a></li>
<li><a href="#">Manual</a></li>
</ul>
<ul class="subMenu">
<li><a href="#">Homepage</a></li>
<li><a href="#">Construct</a></li>
<li><a href="#" class="underSelected">Products</a></li>
<li><a href="#">Community Forum</a></li>
<li><a href="#">Contact Us</a></li>
</ul>
在语义上更正确的是< nav>围绕这两个< ul>单独，还是应该一个导航包？
解决方法
引用规格：
The nav element represents a section
of a page that links to other pages or
to parts within the page: a section
with navigation links.Not all groups of links on a page need
to be in a nav element — only sections
that consist of major navigation
blocks are appropriate for the nav
element. In particular,it is common
for footers to have a short list of
links to varIoUs pages of a site,such
as the terms of service,the home
page,and a copyright page. The footer
element alone is sufficient for such
cases,without a nav element.
所以，请随意包装在一个单一的nav标签。不要包装页脚，但在这里使用页脚标签:)
阅读规格在这里：http://dev.w3.org/html5/spec/Overview.html#the-nav-element
