Example

by Joe Robertson

HTML

<!-- Learn about this code on MDN: https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Positioning/Understanding_z_index/Stacking_context_example_1 -->

<div id="div1">
<br /><span class="bold">DIV #1</span>
<br />position: relative;
   <div id="div2">
   <br /><span class="bold">DIV #2</span>
   <br />position: relative;
   <br />z-index:50;
   </div>
</div>

<br />

<div id="div3">
<br /><span class="bold">DIV #3</span>
<br />position: relative;
   <div id="div4">
   <br /><span class="bold">DIV #4</span>
   <br />position: relative
   ;
   <br />z-index: 42;
   </div>
</div>

</body></html>

CSS

.bold {
    font-weight: bold;
    font: 12px Arial;
}
#div1,
#div3 {
    height: 80px;
    position: relative;
    border: 1px dashed #669966;
    background-color: #ccffcc;
    padding-left: 5px;
}
#div2 {
    opacity: 0.8;
    z-index: 15;
    position: absolute;
    width: 150px;
    height: 200px;
    top: 20px;
    left: 170px;
    border: 1px dashed #990000;
    background-color: #ffdddd;
    text-align: center;
}
#div4 {
    opacity: 0.8;
    z-index: 2;
    position: absolute;
    width: 200px;
    height: 70px;
    top: 65px;
    left: 50px;
    border: 1px dashed #000099;
    background-color: #ddddff;
    text-align: left;
    padding-left: 10px;
}