img.portfolio
{
opacity:1.0;
filter:alpha(opacity=100); /* For IE8 and earlier */
}
img.portfolio:hover
{
	 -o-transition:.5s;
  -ms-transition:.5s;
  -moz-transition:.5s;
  -webkit-transition:.5s;
  /* ...and now for the proper property */
  transition:.5s;
opacity:0.4;
filter:alpha(opacity=60); /* For IE8 and earlier */
}