i using javascript drop down navigation menu found after googling , i've managed style way want. however, after validating site, errors ul tags (error: element ul not allowed child of element ul in context. (suppressing further errors subtree.)). not error, navigation doesn't work way should. i've tried different variations of ul , li tags, , moved things around, , still cannot work correctly. <div class="nav"> <ul id="menu" class="menu"> <li><a href="#">one</a> <ul> <li class="submenu"> <a href="#">one</a> <ul> <li><a href="#">one</a></li> <li><a href="#">two</a></li> <li><a href="#">three</a></li> </ul> </li> <li class="submenu"> ...