Problem with the width of the page using Ahimsa

Hi, i’ve a problem. I’m creating a blog with the theme Ahimsa. The problem is that the page of the blog is too large! I’m trying to modify the widith but i don’t understand what i’ve to modify in the stylesheet 😉
In google or in the forum i don’t finde noone with the same problem… Maybe someone here can help’ me?
this is the stylesheet

/*
Theme Name: Ahimsa
Theme URI: http://ahren.org/code/ahimsa
Description: Ahimsa — basic colours, low graphics, minimal distractions, collapsible sidebar, with rounded corners in Firefox, Safari, Chrome. New for version 2.1: support for WP 2.7 comment system, more consistent look for comments section, many new configurable options (including default visibility of sidebar on posts and pages). Please visit http://ahren.org/code/ahimsa-wp-2dot1 for feature list and to suggest fixes and enhancements.
Version: 2.1
Author: Ravi Sarma
Author URI: http://ahren.org/code/
Tags: green, orange, red, white, yellow, two-columns, flexible-width, left-sidebar, theme-options, threaded-comments

Ahimsa 2.1
http://ahren.org/code/ahimsa

Theme built for the Ahren Code site but free for all
to use. The aim of this theme is to minimise the
distractions to the reader through the use of clean
(mostly) primary colours, low graphics, etc. This
theme uses rounded borders viewable in all browsers
that support them.

The CSS, XHTML and design are released under GPL:
http://www.opensource.org/licenses/gpl-license.php

[huge chunk of code moderated – please use a pastebin]