Help? >.<

[Hall of Famer]

Well if you rename main.css to style.css, it will work for you. Although by doing this, you also need to change the header.tpl file to load style.css, not main.css. This is a minor issue though, as it states that only themes with style.css as its css file can be edited in ACP. Otherwise, you need to edit the theme by simply modifying its file content, not from ACP.