My 960 grid system has wider columns that standard. 55px instead 40px for 16 columns I was surprised to discover my website is wider than is supposed to be.

I am using Drupal + Omega Theme that uses 960 grid system.

The total width of the site is 1180 instead 960.

The columns are wider: 


On 16 columns options: they are supposed to be and 40px they are 55px
On 12 columns options: they are supposed to be 60px and they are 80px.


The gutter is 20px and is ok.

What is the problem?
On wide screens, Omega (or in fact: its base theme 'Alpha') will switch to the wide lay-out. You will find the css for it in alpha/css/grid/alpha_default/wide/alpha-default-wide-16.css and alpha/css/grid/alpha_default/wide/alpha-default-wide-12.css.

This responsive behavior can be controlled from the Omega theme settings page.