960.gs Issue Space between GRID_6 divs to be reduced

Question

I have this code.

/*
  960 Grid System ~ Core CSS.
  Learn more ~ http://960.gs/

  Licensed under GPL and MIT.
*/

/*
  Forces backgrounds to span full width,
  even if there is horizontal scrolling.
  Increase this if your layout is wider.

  Note: IE6 works fine without this fix.
*/

body {
  min-width: 960px;
}

/* `Container
----------------------------------------------------------------------------------------------------*/

.container_12 {
  margin-left: auto;
  margin-right: auto;
  width: 960px;
}

/* `Grid >> Global
----------------------------------------------------------------------------------------------------*/

.grid_1,
.grid_2,
.grid_3,
.grid_4,
.grid_5,
.grid_6,
.grid_7,
.grid_8,
.grid_9,
.grid_10,
.grid_11,
.grid_12 {
  display: inline;
  float: left;
  margin-left: 10px;
  margin-right: 10px;
}

.push_1, .pull_1,
.push_2, .pull_2,
.push_3, .pull_3,
.push_4, .pull_4,
.push_5, .pull_5,
.push_6, .pull_6,
.push_7, .pull_7,
.push_8, .pull_8,
.push_9, .pull_9,
.push_10, .pull_10,
.push_11, .pull_11 {
  position: relative;
}

/* `Grid >> Children (Alpha ~ First, Omega ~ Last)
----------------------------------------------------------------------------------------------------*/

.alpha {
  margin-left: 0;
}

.omega {
  margin-right: 0;
}

/* `Grid >> 12 Columns
----------------------------------------------------------------------------------------------------*/

.container_12 .grid_1 {
  width: 60px;
}

.container_12 .grid_2 {
  width: 140px;
}

.container_12 .grid_3 {
  width: 220px;
}

.container_12 .grid_4 {
  width: 300px;
}

.container_12 .grid_5 {
  width: 380px;
}

.container_12 .grid_6 {
  width: 460px;
}

.container_12 .grid_7 {
  width: 540px;
}

.container_12 .grid_8 {
  width: 620px;
}

.container_12 .grid_9 {
  width: 700px;
}

.container_12 .grid_10 {
  width: 780px;
}

.container_12 .grid_11 {
  width: 860px;
}

.container_12 .grid_12 {
  width: 940px;
}

/* `Prefix Extra Space >> 12 Columns
----------------------------------------------------------------------------------------------------*/

.container_12 .prefix_1 {
  padding-left: 80px;
}

.container_12 .prefix_2 {
  padding-left: 160px;
}

.container_12 .prefix_3 {
  padding-left: 240px;
}

.container_12 .prefix_4 {
  padding-left: 320px;
}

.container_12 .prefix_5 {
  padding-left: 400px;
}

.container_12 .prefix_6 {
  padding-left: 480px;
}

.container_12 .prefix_7 {
  padding-left: 560px;
}

.container_12 .prefix_8 {
  padding-left: 640px;
}

.container_12 .prefix_9 {
  padding-left: 720px;
}

.container_12 .prefix_10 {
  padding-left: 800px;
}

.container_12 .prefix_11 {
  padding-left: 880px;
}

/* `Suffix Extra Space >> 12 Columns
----------------------------------------------------------------------------------------------------*/

.container_12 .suffix_1 {
  padding-right: 80px;
}

.container_12 .suffix_2 {
  padding-right: 160px;
}

.container_12 .suffix_3 {
  padding-right: 240px;
}

.container_12 .suffix_4 {
  padding-right: 320px;
}

.container_12 .suffix_5 {
  padding-right: 400px;
}

.container_12 .suffix_6 {
  padding-right: 480px;
}

.container_12 .suffix_7 {
  padding-right: 560px;
}

.container_12 .suffix_8 {
  padding-right: 640px;
}

.container_12 .suffix_9 {
  padding-right: 720px;
}

.container_12 .suffix_10 {
  padding-right: 800px;
}

.container_12 .suffix_11 {
  padding-right: 880px;
}

/* `Push Space >> 12 Columns
----------------------------------------------------------------------------------------------------*/

.container_12 .push_1 {
  left: 80px;
}

.container_12 .push_2 {
  left: 160px;
}

.container_12 .push_3 {
  left: 240px;
}

.container_12 .push_4 {
  left: 320px;
}

.container_12 .push_5 {
  left: 400px;
}

.container_12 .push_6 {
  left: 480px;
}

.container_12 .push_7 {
  left: 560px;
}

.container_12 .push_8 {
  left: 640px;
}

.container_12 .push_9 {
  left: 720px;
}

.container_12 .push_10 {
  left: 800px;
}

.container_12 .push_11 {
  left: 880px;
}

/* `Pull Space >> 12 Columns
----------------------------------------------------------------------------------------------------*/

.container_12 .pull_1 {
  left: -80px;
}

.container_12 .pull_2 {
  left: -160px;
}

.container_12 .pull_3 {
  left: -240px;
}

.container_12 .pull_4 {
  left: -320px;
}

.container_12 .pull_5 {
  left: -400px;
}

.container_12 .pull_6 {
  left: -480px;
}

.container_12 .pull_7 {
  left: -560px;
}

.container_12 .pull_8 {
  left: -640px;
}

.container_12 .pull_9 {
  left: -720px;
}

.container_12 .pull_10 {
  left: -800px;
}

.container_12 .pull_11 {
  left: -880px;
}

/* `Clear Floated Elements
----------------------------------------------------------------------------------------------------*/

/* http://sonspring.com/journal/clearing-floats */

.clear {
  clear: both;
  display: block;
  overflow: hidden;
  visibility: hidden;
  width: 0;
  height: 0;
}

/* http://www.yuiblog.com/blog/2010/09/27/clearfix-reloaded-overflowhidden-demystified */

.clearfix:before,
.clearfix:after,
.container_12:before,
.container_12:after {
  content: '.';
  display: block;
  overflow: hidden;
  visibility: hidden;
  font-size: 0;
  line-height: 0;
  width: 0;
  height: 0;
}

.clearfix:after,
.container_12:after {
  clear: both;
}

/*
  The following zoom:1 rule is specifically for IE6 + IE7.
  Move to separate stylesheet if invalid CSS is a problem.
*/

.clearfix,
.container_12 {
  zoom: 1;
}

<!DOCTYPE html>
 <head>
  <link rel="stylesheet" type="text/css" href="960_12_col.css">
  <!-- 960 Grid -->
 </head>
 <body>
  <div class="container_12 clearfix">
   
   <div class = "firstRow" style="display:table-row;">
   <!-- Declaration of First Row -->
    <div class="image grid_12" style="display: table-cell;"> 
    <!-- Image Container as DIV -->
     <img src="http://s15.postimg.org/u25xx46tn/NYC.jpg" style="width:100%" />
     <!-- Image Link -->
       </div> 
   </div>
  
   <div class = "grid_12" style = "background-color:blue">
   
   <div class = "grid_6 alpha featureCards" style = "background-color:green; text-align:center;">
    <p>First</p>
   </div>
   <div class = "grid_6 omega featureCards" style = "background-color:yellow; text-align:center;">
    <p>Second</p>
   </div>
   
   </div>
  
  </div>
 </body>
</html>

The html code is shown below

<!DOCTYPE html>
<head>
    <link rel="stylesheet" type="text/css" href="960_12_col.css">
    <!-- 960 Grid -->
</head>
<body>
    <div class="container_12 clearfix">

        <div class = "firstRow" style="display:table-row;">
        <!-- Declaration of First Row -->
            <div class="image grid_12" style="display: table-cell;"> 
            <!-- Image Container as DIV -->
                <img src="http://s15.postimg.org/u25xx46tn/NYC.jpg" style="width:100%" />
                <!-- Image Link -->
            </div>  
        </div>

        <div class = "grid_12" style = "background-color:blue">

        <div class = "grid_6 alpha featureCards" style = "background-color:green; text-align:center;">
            <p>First</p>
        </div>
        <div class = "grid_6 omega featureCards" style = "background-color:yellow; text-align:center;">
            <p>Second</p>
        </div>

        </div>

    </div>
</body>
</html>

See the above code snippet please.

Now, between boxes 'first' and 'second', there is a space that is blue. I want to be able to reduce that space to a smaller width so I can still see the difference between the 'first' and 'second' boxes.

I do NOT want to remove that space! I simply want that blue space to be no bigger than 3 px.

I have tried this for hours, and I can't do it. I also tried to increase the size of the grid_6 boxes but that doesn't work either as they are already self defined. Please is there a solution?

Thanks, Bob.