Default document in IIS8

There are two ways to specify the default document of your site/application

 
Using IIS Manager to specify the default document
Open your site with IIS Manager and double click on the Default Document module. Right click anywhere in the pane and select the "add..." text from the drop down menu. Enter the document name of your choosing. For information on how to connect to your site with IIS Manager, read this Knowledge Base article.


 
Specifying the default document manually
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>