CSS透明滤镜

img{background: #cecece;_background: transparent;filter: alpha(opacity=30);-moz-opacity: 0.3;-khtml-opacity: 0.3;opacity: 0.3;}

img:hover{background: #cecece;_background: transparent;filter: alpha(opacity=100);-moz-opacity: 1;-khtml-opacity: 1;opacity: 1;}