<!DOCTYPE html>编程狮(w3cschool.cn)name="viewport" content="width=device-width, initial-scale=1"rel="stylesheet" href="https://7npmedia.w3cschool.cn/w3.css"class="w3-container"悬停灰度当你将鼠标移动到一个元素上时,w3-hover-grayscale类会给它添加一个“黑白”效果:src="https://atts.w3cschool.cn/img_snowtops.jpg" class="w3-hover-grayscale" alt="Norway" style="width:50%"class="w3-panel w3-red w3-hover-grayscale"悬浮在我上方