I send an http link for mp3 to people, and when they click on it, they complain that the file is playing quictime. Obviously, they need to do "right click" → "save target as", but is there any way to do this for them using javascript?
Unable to execute JavaScript. But there are many ways to do this using server-side scripts. I only know the classic asp: Response.AddHeader "content-disposition", "attachment; filename = fname.ext"
Do you have PHP? http://elouai.com/force-download.php