a:hover img {
　-webkit-opacity: 0.5;
　-moz-opacity: 0.5;
　-o-opacity: 0.5;
　filter: alpha(opacity=50);	/* IE lt 8 */
　-ms-filter: "alpha(opacity=50)"; /* IE 8 */
　opacity: 0.5;
}
 
a img {
　-webkit-transition: opacity 0.3s ease-out;
　-moz-transition: opacity 0.3s ease-out;
　-ms-transition: opacity 0.3s ease-out;
　-o-transition: opacity 0.3s ease-out;
　transition: opacity 0.3s ease-out;
}