Firefox 26.0
download-installer.cdn.mozilla.net
Mac - https://download.mozilla.org/?product=firefox-26.0&os=osx&lang=en-US
Linux - https://download.mozilla.org/?product=firefox-26.0&os=linux&lang=en-US
download-installer.cdn.mozilla.net
Linux - https://download.mozilla.org/?product=firefox-26.0&os=linux&lang=en-US
Generally you want to read the release notes before downloading something. If you're already a Firefox user, it will automatically update, so you don't need to download it manually anyhow. If not, you're probably not just going to want to click on a link on HN to download it. And if you're on anything but Windows, the link to the executable is useless.
Edit to add: ah, I see you posted the other executables in a comment. Still doesn't answer the other questions; it's generally bad form to link straight to an executable on a discussion site like HN.