CSS: transition opacity on mouse-out?

Question

.item:hover {
        zoom: 1;
        filter: alpha(opacity=50);
        opacity: 0.5;
        -webkit-transition: opacity .15s ease-in-out;
        -moz-transition: opacity .15s ease-in-out;
        -ms-transition: opacity .15s ease-in-out;
        -o-transition: opacity .15s ease-in-out;
        transition: opacity .15s ease-in-out;
    }

Why does this only animate the opacity when I hover-in but not when I leave the object with the mouse?

Demo here: http://jsfiddle.net/7uR8z/

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Answer 1

You're applying transitions only to the :hover pseudo-class, and not to the element itself.

.item {   
  height:200px;
  width:200px;
  background:red; 
  -webkit-transition: opacity 1s ease-in-out;
  -moz-transition: opacity 1s ease-in-out;
  -ms-transition: opacity 1s ease-in-out;
  -o-transition: opacity 1s ease-in-out;
  transition: opacity 1s ease-in-out;
}

.item:hover {
  zoom: 1;
  filter: alpha(opacity=50);
  opacity: 0.5;
}

Demo: http://jsfiddle.net/7uR8z/6/

If you don't want the transition to affect the mouse-over event, but only mouse-out, you can turn transitions off for the :hover state :

.item:hover {
  -webkit-transition: none;
  -moz-transition: none;
  -ms-transition: none;
  -o-transition: none;
  transition: none;
  zoom: 1;
  filter: alpha(opacity=50);
  opacity: 0.5;
}

Demo: http://jsfiddle.net/7uR8z/3/