xxxxxxxxxx<html><meta charset="utf-8"><title>编程狮(w3cschool.cn)</title><style> .box{ width:300px; height:200px; margin:0 auto; boxder:1px solid #ccc; background:#000; filter:alpha(opacity:30); opacity:0.3; color:red; }</style><body> <div class="box"></div> <p>opacity:0.3;为关键代码，当opacity值为1时，表示完全不透明，为0时表示完全透明</p></body>