.opacite_css{
  float:left;
  width:30%;
  margin-right:1%;
  padding:5px 1%;
  text-align:center;
  color:#fff;
  background-color:#000;
  font-weight:bold;
}

#opacite_css_1:hover{
  /*
  -webkit : Chrome, Safari, Android
  -khtml : Konqueror
  -moz : Firefox et Mozilla
  -ms : Internet Explorer
  -o : Opera
  */
  -webkit-opacity:0.4;
  -khtml-opacity:0.4;
  -moz-opacity:0.4;
  -ms-opacity:0.4;
  -o-opacity:0.4;
  opacity:0.4;
  filter:alpha(opacity=40);
}

#opacite_css_2:hover{
  background-color:rgba(0,0,0,0.4);
}

#opacite_css_3:hover{
  background-color:rgba(0,0,0,0.4);
  -webkit-transition:background-color 0.3s ease;
  -khtml-transition:background-color 0.3s ease;
  -moz-transition:background-color 0.3s ease;
  -ms-transition:background-color 0.3s ease;
  -o-transition:background-color 0.3s ease;
  transition:background-color 0.3s ease;
}