If Chrome DevTools is reporting a 404 for a .map file (maybe
jquery-2.0.3.min.map, but can happen with anything) first thing to know is this is only requested when using the DevTools. Your users will not be hitting this 404.
Now you can fix this or disable the sourcemap functionality.
Fix: get the files
Next, it's an easy fix. Head to http://jquery.com/download/ and click the Download the map file link for your version, and you'll want the uncompressed file downloaded as well.
Having the map file in place allows you do debug your minified jQuery via the original sources, which will save a lot of time and frustration if you don't like dealing with variable names like
Dodge: disable sourcemaps