How to Make ASP.Net process .html Files through IIS? 

By switching the website’s application pool to the ‘Integrated’ mode, you can force ASP.Net to process.html files via IIS.

To switch the application pool through IIS to integrated mode, follow these instructions.

1. Click on Start >> Administrative Tools >> IIS Manager.

1. In Connections Windows, click on the server’s name and expand it.

1. Now expand the Sites option.

1. Select the website in question and right-click on it.

1. Under the Manage website, select Advanced Settings.

1. Click on the application pool and select the Application pool with integrated from the drop-down.

1. Click OK.

1. Restart your website.