?0dcd3e at the end of each media, css and js file

It is coming from the cache plugin. If you look under Browser Cache settings, you will see an option:

Prevent caching of objects after settings change
Whenever settings are changed, a new query string will be generated and appended to objects allowing the new policy to be applied.

If you uncheck that, the string will no longer be appended to your media. However, I would keep it there, it’s useful for forcing people’s browser caches to load fresh css, js, images, etc.