The Default Documents Tool allows you to choose the file name for your startup page.  You can either add (and prioritize) your own file name or choose what is on the list.

Manually Coding Your Default Documents in Your Application's web.config File

This process varies based on whether the Site or Application has an existing web.config file.

If the web.config File Exists

Open the existing web.config file and place the following code between the lines of <system.webServer> and </system.webServer>.  Replace the section "index.html" with the document of your choosing.

<defaultDocument>
  <files>
    <clear/>
    <add value="index.html"/>
  </files>
</defaultDocument>

If the web.config File Does Not Exist

If there is no web.config file for the site or application root, place the following code inside a text document.  Replace the section "index.html" with the document of your choosing.   Save the file and name it web.config, then upload it to the root folder of your site or application with your preferred FTP application.

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
  <system.webServer>
    <defaultDocument>
      <files>
        <clear/>
        <add value="index.html"/>
      </files>
    </defaultDocument>
  </system.webServer>
</configuration>