There are some comments below the documentation that are essentially important to help users to troubleshoot problems when integrating with IIS. Some of those comments are:

If you get 400 Bad Request exceptions from your JIRA installation when running behind IIS try adding a web.config to the JIRA IIS folder with the following:

<system.webServer>
<httpErrors errorMode="Detailed" />
</system.webServer>

And:

Please note that if the IIS 7 role/feature "HTTP Errors" is installed, IIS does not forward the "custom" error pages from JIRA / Confluence and instead displays its own error page, e.g. on 401 (unauthorized) or 404 (not found) errors. This is a problem in particular when those custom errors are being processed by JavaScript (e.g. after clicking a button on a page), since the actual error reason is then obviously "being lost by IIS".

To cut it short: If you don't need it for anything else, remove the "HTTP Errors" on IIS 7.

It will make it much easier for the users to troubleshoot their integration if some of those comments were included in the document.