51help TIY
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"> h1:before {content:url(/i/51help_logo_white.gif)} </style> </head> <body> <h1>This is a heading</h1> <p>The :before pseudo-element inserts content before an element.</p> <h1>This is a heading</h1> <p><b>注释：</b> !DOCTYPE，那么 Internet Explorer 8 content 属性。 </body> </html>
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