The Clean Green theme is a nice minimalistic theme that is well suited for business applications and where a fast loading theme is a must. The theme uses a standard full-width, three-column layout with soft green accents.

The Clean Green FW theme is a fixed-width (768px) variation of the Clean Green theme. The Clean Green FW theme works best on two-column layouts, but does support three-column layouts.

If you wish to have a three-column layout, but you find that on some pages the layout breaks, try adjusting your block preferences so that the right column blocks do not display on that page.

Links:
Clean Green Theme
Clean Green FW Theme

Enjoy!

JMorris