How to Read IIS Errors
IIS error pages show a status code plus a sub-status, such as 500.19. The sub-status is the real clue. Always note the full code and the error text before you start changing settings. Below are the three errors our support desk sees most often on customer Windows servers.
Error 500.19 — Configuration Data Is Invalid
This means IIS cannot read the web.config file for the site. Common causes and fixes:
- Locked section. The config uses a section that is locked at server level. The error page names the section. Unlock it in Configuration Editor or remove that block from web.config.
- Missing module. The config references URL Rewrite or another module that is not installed. Install the module or delete the rewrite block.
- Bad XML. A typo or an unclosed tag breaks the file. Validate the XML in a code editor.
- Permissions. Make sure IIS_IUSRS can read the site folder and the web.config file.
Error 502.5 — ASP.NET Core Process Failure
The ASP.NET Core module started your application but the process failed. Check these items in order:
- Confirm the correct .NET Hosting Bundle version is installed for your application.
- Run the application manually with the dotnet command in a terminal to see the real startup error.
- Check the Windows Event Viewer application log for stdout messages.
- Restart the application pool after installing any hosting bundle.
Error 403.14 — Directory Listing Denied
IIS found the folder but no default document. Either add a default document such as index.html to the Default Document list for the site, or confirm your application files were actually deployed to the correct folder. This error very often means the site is pointing at an empty or wrong directory.
If the error persists, open a support ticket with a screenshot of the full error page and we will investigate on the server.
