W3School TIY
编辑您的代码：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html> <head> <style type="text/css"> img[alt] { border: 5px solid red; } </style> </head> <body> <h1>可以应用样式：</h1> <img src="../i/w3school_logo_black.gif" alt="W3School Logo" /> <hr /> <h1>无法应用样式：</h1> <img src="../i/w3school_logo_black.gif" /> </body> </html>
查看结果: