Source mapping is a technique that "maps" your browser inspector's line numbers to the source file. This is useful when working with assets that are compiled from LESS, SASS, Coffeescript and so on. Source maps can also be used with minified assets that would normally have their line numbers removed. If you're curious, here's some more information regarding source maps.
- Open Developer Tools.
- Mac users: View > Developer > Developer Tools.
- Click the Settings cog icon in the upper-right corner of the Developer Tools window.
- Under the Sources section, check the box(es) for the source maps you want to enable.