error when adding a default page to web.config

I have 1 webpage with a SQL connection. When I run on localhost on Windows 7, this error occurs.

HTTP Error 500.19 - Internal Server Error

The requested page cannot be accessed because the related configuration data for the page is invalid.

Config Error Cannot add duplicate collection entry of type 'add' with unique key attribute 'value' set to 'default.aspx'

Config File \?\D:\SIPLWEB\WebSite\web.config

 120:             <files>
 121:                 <add value="default.aspx开发者_运维问答" />
 122:             </files>

You already have "default.aspx" as the default document at a higher level, most likely in your iis config, it's added by default. You can find it in your applicationHost.config file.

You can remove the default document entry from your web.config file and it will work.