Width of the Mainpage

Hello
first I’d like to thank you for this awesome template you made. I’m using it for making a portfolio site for personal works. (because I have to look for a new job 😉

one thing that I’d like to change is the maximum width of the site. As it seems to me its max width now is “span12”. But i’m not shure.

Do you have a hint where i can define this variable?

Thanks for helping. Greetings
JM