This can help understand the basics of the 960's grid structure. This framework is based on a very simple principle that combines fixed widths and margins to create a grid, such as a layout for quick site development. The entire infrastructure used float: left , which allows the sides to display side by side, as well as create a 20px buffer between each grid. And so I believe that you do not understand the use of the "alpha" and "omega" classes. These classes are designed to remove fields on grids that are children of other grids in order to multiply the margin.
Take this code, for example:
<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8" /> <title>960 Grid System — Demo</title> <link rel="stylesheet" href="css/reset.css" /> <link rel="stylesheet" href="css/text.css" /> <link rel="stylesheet" href="css/960.css" /> </head> <body> <div class="container_12" style="background:blue;"> <div class="grid_3 alpha" style="background:yellow;">Grid_3 Alpha</div> <div class="grid_9 omega" style="background:green;">Grid_9 Omega</div> </div> </body> </html>
This creates something similar:
you will notice that there is no field to the left of Grid_3, but there is a 20-pixel margin between Grid_3 and Grid_9. This is called Grid_3 having margin-right:10px and Grid_9 with margin-left:10px . When both divs float to the left, they create that distance. You will also notice that there is another 10px margin to the right of Grid_9. This is due to the fact that the left margin was deleted in Grid_3 and now the whole layout is shifted over 10px inside div_ container_12.
In order to describe the layout. Which from my understanding should look like this: 
You will need to either create a new class to apply float:right to Grid_9, or increase the width of Grid_9.
For this, inline will look something like this:
<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8" /> <title>960 Grid System — Demo</title> <link rel="stylesheet" href="css/reset.css" /> <link rel="stylesheet" href="css/text.css" /> <link rel="stylesheet" href="css/960.css" /> </head> <body> <div class="container_12" style="background:blue;"> <div class="grid_3 alpha" style="background:yellow;">Grid_3 Alpha</div> <div class="grid_9 omega" style="float:right; background:green;">Grid_9 Omega</div> </div> </body> </html>
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