Source URLs are awesome little 'meta comments' that the browser can use for finding the names of scripts. For example:
//@ sourceURL=my/script/name
This means that instead of seeing one compiled file in Chrome's inspector, like this:
You see your whole directory tree:
So much easier to navigate! The alternative to this is to spit out multiple script tags into the page.
Just require sprockets/source_url in development.
Both Chrome and Firefox have @sourceURL support. For more information, please see this excellent post on the subject.