The MimeType needs to be attached to the hyperlink. No MimeType attached, and Firefox won't guess what the file is - the user needs to select the application manually.

Then how do I manually tell Firefox to save text files instead of automatically displaying them? There's no "text/plain" type for me to edit listed on the Applications tab. Screenshot attached showing the page info for one of the spk files and the Applications tab with no "text" type listed. There's another at here. I don't care if the web server owner has attached the wrong MIME type to a file so long as Firefox will give me a chance to tell it how I want it to be handled. If it's not a webpage (html, php, etc.) then Firefox should not try to render it by itself without asking. --- On a side note, how do I get this forum to treat my line returns like line returns rather than spaces?

If the server sends a file as text/plain then Firefox will open the file in a tab instead of offering to download the file.

You can use "Save Link as" in the right-click context menu or set the browser.altClickSave pref to true on the about:config page. In the case of the latter you can hold don the Alt key and left-click a link to get a download dialog.

See also:

• http://kb.mozillazine.org/File_types_and_download_actions

• https://support.mozilla.org/kb/Managing+file+types
• https://support.mozilla.org/kb/change-firefox-behavior-when-open-file

Neither of those will work in some cases. For example, go here and try to download the spk for version 4.07. It's not possible with Firefox. I'd have to click it, copy the address for the file it opens, post the address somewhere else as a link, and then right click that link to get the "Save Link as" dialog. Internet Explorer asks me what to do with the file instead of just rendering it; can't Firefox be made to do something so simple?

Yes, in cases like this where JavaScript (onclick) is used you can not use the above posted possibilities.
Luckily in this case there is a workaround possible.

The links are defined directly in the source code of that page in the function downloadfile(fileno, counter)

If you inspect the page source by prefixing the URL with the view-source: protocol then you can select the link URL with the mouse and use "Save Link as" in the right-click context menu to save the spk file.

• view-source:http://www.tecsg.co.uk/scs/index.php
• http://www.tecsg.co.uk/scs/scs407.spk

So, there's no way to do what I want... configure Firefox to ask what to do with text/plain files instead of rendering them. I've dropped a feature request for this into the suggestion box.