Say this is your Navigation code:
<ul class="mainMenu">
<% control Menu(1) %>
<li class="liMainMenu">
<a href="$Link" title="Go to the $Title.XML page" class="$LinkingMode aMainMenu">$MenuTitle.XML</a>
<% if children %>
<ul class="subMenu1">
<% control children %>
<li class="liSubMenu1"><a href="$Link" title="Go to the $Title.XML page" class="$LinkingMode aSubMenu1">$MenuTitle.XML</a></li>
<% end_control %>
</ul>
<% end_if %>
</li>
<% end_control %>
</ul>
You would want to change it to this:
<ul class="mainMenu">
<% control Menu(1) %>
<li class="liMainMenu">
<% if children %>
<span class="$LinkingMode aMainMenu">$MenuTitle.XML</span>
<ul class="subMenu1">
<% control children %>
<li class="liSubMenu1"><a href="$Link" title="Go to the $Title.XML page" class="$LinkingMode aSubMenu1">$MenuTitle.XML</a></li>
<% end_control %>
</ul>
<% else %>
<a href="$Link" title="Go to the $Title.XML page" class="$LinkingMode aMainMenu">$MenuTitle.XML</a>
<% end_if %>
</li>
<% end_control %>
</ul>