I recently refactored the main css for the mobile version of the company I work at. I inherited the project and noticed that the main CSS file had 155kb compressed and it had lots of sections that were already removed from the website and duplicated or triplicated attributes that were added when new features or fixes and updates were added.
I changed it to SASS and also documented everything so if some one else than me needs to work on this knows easily what to do. This kind of thing happens a lot when you have many people working on the same project.
By the end of the task I was able to reduce the file to 59kb.