<html><head><style>img:hover { opacity: 0.5;}</style></head><body><h1>图像透明度</h1><p>opacity 属性常与 :hover 选择器一起使用，改变鼠标悬停时的不透明度：</p><img src="/i/photo/tulip.jpg" alt="Tulip" width="170" height="170"><img src="/i/photo/tulip-2.jpg" alt="Tulip" width="170" height="170"><img src="/i/photo/flower-4.jpg" alt="Flower" width="170" height="170"></body></html>