I tested your scenario by adding custom html file inside a folder named “CustomPages” . This folder should be placed on the root level of your project – where is the web.config file. Then you can access it through the url similar to the following:
If this doesn’t work in your scenario please make sure that you don’t have any limitation of the allowed file extensions in your IIS. Please have in mind that we handle in a special way request coming from folders with a certain names (like “Sitefinity”, “Images”, etc) so this could restrict you for accessing your files.
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