In the html we always use <script type="text/javascript" charset="utf-8" src="???"></script> (the ECMA stuff confuses some browsers) but on the HTTP side what are you meant to use as the Content-Type?
By instinct this would also be text/javascript, but Apache uses application/javascript and Amazon uses application/x-javascript.
Some firewall admins block any MIME types matching application/*; but which MIME type are you meant to use from a webmaster perspective? What is the "right" thing to do.