W3Schools 在线编辑工具（TIY） V3.0
编辑的代码:
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<!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"> p[class~="important"] { color: red; } </style> </head> <body> <h1>可以应用样式：</h1> <p class="important warning">This is a paragraph.</a> <p class="important">This is a paragraph.</a> <hr /> <h1>无法应用样式：</h1> <p class="warning">This is a paragraph.</a> </body> </html>