#blue {

  background-color: blue;

  z-index: 3;

}

​

#red {

  background-color: red;

  z-index: 2;

}

​

#green {

  background-color: green;

  z-index: 1;

}

z-index => allows you to LAYER your components

z-index: 2147483638 is the maximun "height" you can give your component

otherwise it will not work

z-index: -1;

/* The z-index property specifies the stack order of an element. */

.z-index {

   z-index: -1;

}

You can do this, but only if the parent doesn't have a 

position: relative or absolute property on it. 

So if you remove the position: absolute from the 

first div, it'll work as expected.

Child with z-index 9999 and parent z-index of 3 will lose to a child with z-index 1 and parent with z-index of 4