[html] How to make div appear in front of another?

Please refer to the codes below :

<ul>
 <li style="height:100px; overflow:hidden;">
  <div style="height:500px; background-color:black;">
  </div>
 </li>
</ul>

From the codes above, we know that we can only see 100px height of black background. My question is how can we see 500px height of <div> black background? In other words, how can I make the <div> appear in front of <li> ?

The black div will display the full 500px unless overflow:hidden is set on the 100px li

I think you're missing something.

http://jsfiddle.net/ZNtKj/

<ul>
 <li style="height:100px;overflow:hidden;">
  <div style="height:500px; background-color:black;">
  </div>
 </li>
</ul>
<ul>
 <li style="height:100px;">
  <div style="height:500px; background-color:red;">
  </div>
 </li>
</ul>

In FF4, this displays a 100px black bar, followed by a 500px red block.

A little bit different example:

http://jsfiddle.net/ZNtKj/1/

<ul>
 <li style="height:100px;overflow:hidden;">
  <div style="height:500px; background-color:black;">
  </div>
 </li>
</ul>
<ul>
 <li style="height:100px;">
  <div style="height:500px; background-color:red;">
  </div>
 </li>
 <li style="height:100px;overflow:hidden;">
  <div style="height:500px; background-color:blue;">
  </div>
 </li>
 <li style="height:100px;overflow:hidden;">
  <div style="height:500px; background-color:green;">
  </div>
 </li>
</ul>

You can set the z-index in css

<div style="z-index: -1"></div>

Upper div use higher z-index and lower div use lower z-index then use absolute/fixed/relative position

In order an element to appear in front of another you have to give higher z-index to the front element, and lower z-index to the back element, also you should indicate position: absolute/fixed...

Example:

<div style="z-index:100; position: fixed;">Hello</div>
<div style="z-index: -1;">World</div>