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<!doctype html> <html lang="vi"> <head> <meta charset="utf-8"> <title>Học web chuẩn</title> <script src="https://code.jquery.com/jquery-latest.js"></script> <script> $(function(){ $('#test').css('border','1px solid blue'); }); </script> </head> <body> <div id="test">div</div> <p>p</p> <div> <p>p bên trong div</p> </div> </body> </html>