On Windows, I would suggest checking whether the files have a .ai extension on the name; I'm not sure that is needed on Mac. (Also, I suppose it could be a different kind of file.)

Are the files opening in Adobe Illustrator or in another application?

If instead of right-clicking the files on the site you left-click them, does Firefox display a dialog indicating what type of content Firefox thinks it is?

The files all have the .ai extension, I operate Mac. They are opening in Illustrator with the coding text, and they save as a thumbnail of the AI logo (they used to save as a thumbnail of the art the original creator made). I can left click and choose the option to "Save to downloads", which lets me still do my work. The right clicking method was just most convenient and out of curiosity I'd like to fix it. I attached a picture of what the saving and opening windows look like, if it helps.

Moderator note: I removed the image because it contains your address. Feel free to post again with this information removed.

I think it's a problem that the dialog says the format is HTML instead of whatever .ai normally says. It's almost as though you are saving a browser-based preview of the document rather than the actual document. Does the site hosting the files offer a download button or other method to get the file in its original format?

Right and left clicking are my only download options (I've been left clicking to get around the problem. Still inconvenient, but at least I can work). I went into Firefox's preferences to adjust the "applications" section, and I don't even see AI files as an option. My coworker's trying to help, but we're both stumped.

I should have asked before...

On the right-click menu, are you using:

• Save Link As
• Save Page As

Save Link As works like left-clicking a link but skips directly to the Save dialog. (Mostly -- there are some cases where the link redirects and Save Link As doesn't follow it far enough.)

Save Page As saves the current page which, it sounds like, is a preview rendering of the .ai file and not the file itself.

When I right click, I use "Save Link As". It used to work fine, just saving it to the desktop. Left clicking is the option to open/save, I see this window. I'm so confused as to why the right clicking method worked forever, and one day it just starts malfunctioning like this. I didn't change any settings, I didn't even access the settings until the problem occurred.

Hmm, I don't know. Maybe it's a change in Firefox 38 causing different results for some reason?

If you compare the link in the page with the link in the Downloads list, can you see any redirect occurring?

• In page (prior to clicking): right-click the link > Copy Link Location, and paste into a text document
• In Downloads list (post-download): right-click the download > Copy Download link, and paste below the other link