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"> input:focus { background-color:yellow; } </style> </head> <body> <form action="http://www.51help.tk/tiy/form_action.asp" method="get"> First name: <input type="text" name="fname" /><br /> Last name: <input type="text" name="lname" /><br /> <input type="submit" value="Submit" /> </form> <p><b>注释：</b> !DOCTYPE，那么 Internet Explorer 8 :focus 伪类。</p> </body> </html>
查看结果: