Source maps (http://www.html5rocks.com/en/tutorials/developertools/sourcemaps/) are basically a way to map a combined/minified file back to an unbuilt state. To avoid error messages in Browser DevTools, source map files should be served with the MIME type "application/json"
{ "ma", "application/mathematica" },
{ "nb", "application/mathematica" },
{ "mb", "application/mathematica" },
+ { "map", "application/json" },
{ "mathml", "application/mathml+xml" },
{ "mbox", "application/mbox" },
{ "mscml", "application/mediaservercontrol+xml" },