Fresh Green is a lightweight theme based on Omega, which means it is a responsive HTML5 theme.
The theme has been conceived to be the theme of my personal blog but I've decided to open it.
As this theme is based on Omega, you must have Omega on your themes folder but you don't need to enable it.
There are some problems when you are not using the latest version of modern browsers. I have only tested the layout with Firefox > 12, Chrome and IE > 9.
If you are a CSS expert and want to fix it, you are very welcome. Otherwise have in mind I will not spend much effort on it by myself.