The main.css is generated from the SASS (in its dialect SCSS) files. Please do not edit the CSS-files in any case but search the correct .scss file and edit the according SCSS. If you are not familiar with SCSS you can write pure CSS which is actually valid SCSS.

See http://wiki.typo3.org/Sass for details.


When you have SASS working, execute the following command to compile CSS file from within this directory:

$ sass ../../Private/Scss/main.scss main.css