How do I download a mp3 file from my broswer in OSX?

Solution 1:

It depends on the browser's terminology, but when you right click an mp3 link there will be an option such as Save Link As... or Save Target As... or Save Linked File As.... This option will allow you to save the file rather than having the browser attempt to play it with the default application.

Solution 2:

Also, it depends on what the browser is set to do with that particular type of file. For instance, see in Firefox, Tools > Options > Applications tab.

(Feel free to expand my answer here. I think some more could be said about browsers and MIME types - not that I really know much about it.)