关于网站伪静态的问题？

http://zhuangbox.com/index_5.html 这是什么情况？

web.config文件:<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<system.webServer>
<rewrite>
<rules>
<rule name="Rewrite to show.php">
<match url="^show/([0-9]+).html" />
<action type="Rewrite" url="show.php?tid={R:1}" />
</rule>
<rule name="Rewrite to index.php">
<match url="^index_([0-9]+).html" />
<action type="Rewrite" url="index.php?p={R:1}" />
</rule>
</rules>
</rewrite>


</system.webServer>
</configuration>