下拉菜单子菜单居中

Question

I was adapting a css stylesheet for a dropdown-menu. I am having troubles with centering the boxes for the sub-menu. It currently looks like

#nav{
  list-style:none;
  margin:0;
  padding:120px 100px;
  text-align:center;
}
#nav li{
  position:relative;
  display:inline;
}
#nav a{
  display:inline-block;
  padding:10px;
}
#nav ul{
  position:absolute;
  left:-9999px;
  margin:0;
  padding:0;
  text-align:center;
}
#nav ul li{
  display:block;
}
#nav li:hover ul{
  left:0;
}
#nav li:hover a{
}
#nav li:hover ul a{
  text-decoration:none;
  background:none;
}
#nav li:hover ul a:hover{
  background:#fff;
}
#nav ul a{
  white-space:nowrap;
  display:block;
}
a{
  color:#c00;
  text-decoration:none;
  font-weight:bold;
}
a:hover{
}

But I would like that the sub-boxes are centered with respect to the box on the higher level. How Can I achieve that?

Answer 1

• Make immediate (top level) li s into relative containers
• Left position nested ul s 50% within the newly-defined relative container and translate them -50% of their own size
• Remove left:-9999px; on nested ul s and toggle display: none / block

 #nav > li { position: relative; } #nav { list-style: none; margin: 0; padding: 20px 100px; text-align: center; } #nav li { position: relative; display: inline; } #nav a { display: inline-block; padding: 10px; } #nav ul { display: none; position: absolute; margin: 0; padding: 0; left: 50%; transform: translateX(-50%); } #nav ul li { display: block; } #nav li:hover ul { display: block; } #nav li:hover a {} #nav li:hover ul a { text-decoration: none; background: none; } #nav li:hover ul a:hover { background: #fff; } #nav ul a { white-space: nowrap; display: block; } a { color: #c00; text-decoration: none; font-weight: bold; }

 <ul id="nav"> <li><a href="#">One</a> <ul> <li><a href="#">Sub One</a></li> <li><a href="#">Sub Two</a></li> </ul> </li> <li><a href="#">Two</a> <ul> <li><a href="#">Sub One</a></li> <li><a href="#">Sub Two</a></li> </ul> </li> <li><a href="#">Three</a> <ul> <li><a href="#">Sub One</a></li> <li><a href="#">Sub Two</a></li> </ul> </li> </ul>

jsFiddle