Are you saving the files as text files or as "Web page, HTML only"?

I'm selecting save as textfile. What Firefox is actually doing I'm not sure. Could even be a Windows setting that's causing the readability problems. Someone told me it's because the files I'm saving are on the Web as Unix. All I know is that Explorer saves them as readable textfiles. Firefox saves them as something that looks like a bizarre spreadsheet. And this can't be a common problem or there would be threads about it.

Unix line endings are only a linefeed character (%0A; \n).
Windows uses a Carriage Return (%0D; \r) and linefeed (%0A; \n) combination as line ending.
So if the text files get saved with only a linefeed then you will see a long line.

What do you get when you open such a text file in Firefox (file extension needs to be .txt)?

Not sure what you're asking. I'm at a website (like ScienceDaily) while using Firefox, reading one of their articles/ press releases. The article looks perfectly normal. I save it as a textfile. Later, when trying to read the article offline, I see what you describe--long, seemingly endless lines of text. If the same file had been saved by Explorer, it would read like a normal text file.

So how do I tell Firefox to add a carriage return at the end of each line when saving a textfile? Isn't this standard behavior?

You know, this has been going on so long I've forgotten what actually happens and just accepted that Firefox does not save text documents properly. I use another browser for saving textfiles.

I just tried again and Firefox saved an article as an htm file, even though the choice was "save as textfiles." So maybe the fix is somewhere in options. Beats me.