<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>无标题文档</title> <script type="text/javascript"> document.write("你好啊！"); var a = "1"; a=a+4; function aa() { document.write(a); } </script> </head> <body> <font size="+4">今天是星期五！</font> <input type="button" value="提交" onclick="aa()" /> </body> </html>