SharePoint Site Canvas Fix with Regarding of Screen Resolution

Hi, I had issue SharePoint 2010 Out of the Box SharePoint default theme. As you see below Announcement, Leadership Message, Feature Story and other webparts had no fix width and my computer screen resolution is full HD 1920 x 1080. The webpart dynamically shrink to fix the content.

Based on the business requirement, the webpart zone should had fix with so I set the width 480 pixel for Announcement, Leadership Message, Feature Story...However, with 1920 x 1080, it create too much white space between the webparts

My goal is to have the nice display below screen which have tied/fix width between the webpart regardless of screen size resolution in case other users use different resolutions 1440x800 or 1024 x 768 or users resize the their browser.

I know that I had to create custom css and modify certain css property to achieve the above goal. Please give me directions how to do it and what line of code I have to change in CSS.

Thanks