keep this into your web config file then rename the add value=”yourwebformname.aspx”
<system.webServer>
<defaultDocument>
<files>
<add value="insertion.aspx" />
</files>
</defaultDocument>
<directoryBrowse enabled="false" />
</system.webServer>
else
<system.webServer>
<directoryBrowse enabled="true" />
</system.webServer>