おわり。
0.3sとかいじると変化する速さ変えられるよ。
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;
}