You need to either set the default browser as Firefox or go into Settings -> System -> Default Apps in Windows 10 and change the .htm & .html protocols to open in Firefox.

Pardon my ignorance, but I cannot find any default app anywhere that refers to .htm or .html.

Sorry, I just had you go to the Default apps section. You need to scroll down and click "Choose default apps by file type"

Apparently, I misstated my original problem. The problem is that I am receiving emails that request me to DOWNLOAD an html/ htm document. Firefox refuses to DOWNLOAD the app. Please help me resolve this. I can easily download it in Edge.

billyj500 said

The problem is that I am receiving emails that request me to DOWNLOAD an html/ htm document. Firefox refuses to DOWNLOAD the app.

Please describe this in a more step-by-step manner if you can: what do you do, and what error message(s) do you get?

• Is the HTML document an attachment to the email message, or something Firefox needs to retrieve from a different website?

• What do you get when you click the link or button to download the HTML document?

It's an attachment at the bottom. The paperclip says "no preview" and "Download". When I press "download," nothing happens.

But download works normally for other kinds of files?

If you check Firefox's downloads button on the toolbar, does it indicate any issues with the download? Sometimes downloads are blocked due to residing on an untrustworthy site, for example.

Firefox 42+ has a Tracking Protection feature that is enabled by default in Private Browsing mode. Firefox can show a shield icon at the left end of the location/address bar that some content is blocked by Tracking Protection, click the shield icon for more information.

You can check the Web Console (Tools -> Web Developer) for messages about blocked content and about the presence of mixed or unsafe content.

• https://developer.mozilla.org/en/Tools/Web_Console
• https://support.mozilla.org/en-US/kb/mixed-content-blocking-firefox