<html><head><style>img { opacity: 0.5;}img:hover { opacity: 1.0;}</style></head><body><h1>图片透明度</h1><p>opacity 属性通常与 :hover 选择器一起使用来改变鼠标悬停时的不透明度：</p><img src="img_forest.jpg" alt="森林" width="170" height="100"><img src="img_mountains.jpg" alt="山脉" width="170" height="100"><img src="img_5terre.jpg" alt="Italy" width="170" height="100"></body></html>