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<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>本教程(w3big.com)</title> </head> <body> <button type="button" autofocus onclick="alert('Hello world!')">点我</button> <p><strong>注意:</strong> Internet Explorer 9 以及更早 IE 版本不支持 autofocus 属性。</p> </body> </html>