Now attached.

You can't add file type yourself in "Options/Preferences -> Advanced". Firefox will add an entry automatically if you tick the checkbox in that open with dialog.

Note that such a setting is always linked to a specific MIME (content) type and is disbled when the server sends the file with a generic content type (application/octet-stream) or via a content disposition header.

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

thanks that it good to know. not sure if you have also seen my other question posted at URL below. Summary is for my SAAS users cannot download files in Firefox; a blank tab just shows up. But it works in IE and Chrome on my SAAS. Users are also able to download files from other sites in Firefox just not my SAAS.

https://support.mozilla.org/en-US/questions/1165399