How do I change page width to 970px?

You could use http://www.spry-soft.com/grids/ to generate a grid that has your width in it with appropriate gutter widths and column widths (but 970 might be hard to accomplish) and overwrite the 960.css file with that. (not by editing the default on in omega, but by including your own which will take precedence over the original)

The 3.x version (which is in the works now) will allow for completely customizable grids via extending the subtheme with support for multiple grids (for responsive layouts) via defining your own grids.

Hi, I did that a few days ago.
Basically I created a custom grid (32-columns, 992px) as himerus suggests, then I just did the following:

1. I included it in my subtheme's .info file this way:

; ------- Declare default stylesheets
stylesheets[all][] = css/subtheme.css
stylesheets[all][] = css/992.css

2. I replaced all the '_' with '-' in 992.css to make all the classes match the omega standard ones.

3. altered the theme settings form (in subtheme's theme-settings.php file) to make it match the new layout "features" (ie: printing 982px of usable space in the select box instead of the standard 960px) this way: http://pastebin.com/Jvqe5Hed

It's not a completely clean solution, I could have add the layout to the existing ones so that all of them would have been still available, but this 'hack' works fine for me and at least I have some "tracking" of the non-standard behavior (the 992px grid) in the UI of the theme settings.

I hope it helps

Thanks for the tutorial himerus and omissis. Works very well on 6.x as well :)

Bookmarking, greetings, Martijn