EDIT

/**

 * @file

 * Positioning for responsive layout .

 *

 * Define CSS classes to create a table-free, 3-column, 2-column, or single

 * column layout depending on whether blocks are enabled in the left or right

 * columns.

 *

 * This layout uses the Zen Grids plugin for Compass: http://zengrids.com

 */

@import "base";

// We are going to create a 980px wide, 5 column grid with 20px gutters between

// columns (applied as 10px of left/right padding on each column).

$zen-column-count:  5;

$zen-gutter-width:  40px;

// IE6-7 don't support box-sizing: border-box. We can fix this in 1 of 3 ways:

// - Drop support for IE 6/7. :-) In the _base.scss, set $legacy-support-for-ie6

//   and $legacy-support-for-ie7 to false.

// - (Preferred) Install the box-sizing polyfill and set the variable below to

//   the absolute path URL to the boxsizing.htc file.

//   @see https://github.com/Schepp/box-sizing-polyfill

//   $box-sizing-polyfill-path: "/path/to/boxsizing.htc";

// - Use the same CSS unit for grid width and gutter width (use px for both or

//   use % for both, etc.) and set the box-sizing variable to content-box.

//   $zen-box-sizing: content-box;

// You can generate more efficient CSS if you manually apply the

// zen-grid-item-base mixin to all grid items from within a single ruleset.

$zen-auto-include-item-base: false;

// $zen-auto-include-flow-item-base: false;

/*

 * Center the page.

 */

#page,

.region-bottom {

  /* For screen sizes larger than 1200px, prevent excessively long lines of text

     by setting a max-width. */

  margin-left: auto;

  margin-right: auto;

  max-width: 960px;

}

/*

 * Apply the shared properties of grid items in a single, efficient ruleset.

 */

// See the note about $zen-auto-include-item-base above.

#header,

#content,

#navigation,

.region-sidebar-first,

.region-sidebar-second,

#footer {

  @include zen-grid-item-base();

}

/*

 * Containers for grid items and flow items.

 */

#header,

#main,

#footer {

  @include zen-grid-container();

}

/*

 * Navigation bar

 */

@media all and (min-width: 480px) {

  #main {

    padding-top: $menu-bar-line-height + $zen-gutter-width; /* Move all the children of #main down to make room. */

    padding-bottom: $zen-gutter-width;

    position: relative;

  }

  #navigation {

    position: absolute;

    top: 0; /* Move the navbar up inside #main's padding. */

    height: $menu-bar-line-height * 2;

    width: $zen-grid-width;

  }

}

@media all and (min-width: 480px) and (max-width: 959px) {

  /*

   * Use 3 grid columns for smaller screens.

   */

  $zen-column-count: 3;

  /*

   * The layout when there is only one sidebar, the left one.

   */

  .sidebar-first {

    #content { /* Span 2 columns, starting in 2nd column from left. */

      @include zen-grid-item(2, 2);

    }

    .region-sidebar-first { /* Span 1 column, starting in 1st column from left. */

      @include zen-grid-item(1, 1);

    }

  }

  /*

   * The layout when there is only one sidebar, the right one.

   */

  .sidebar-second {

    #content { /* Span 2 columns, starting in 1st column from left. */

      @include zen-grid-item(2, 1);

    }

    .region-sidebar-second { /* Span 1 column, starting in 3rd column from left. */

      @include zen-grid-item(1, 3);

    }

  }

  /*

   * The layout when there are two sidebars.

   */

  .two-sidebars {

    #content { /* Span 2 columns, starting in 2nd column from left. */

      @include zen-grid-item(2, 2);

    }

    .region-sidebar-first { /* Span 1 column, starting in 1st column from left. */

      @include zen-grid-item(1, 1);

    }

    .region-sidebar-second { /* Start a new row and span all 3 columns. */

      @include zen-grid-item(3, 1);

      @include zen-nested-container(); // Since we're making every block in this region be a grid item.

      @include zen-clear();

      .block {

        @include zen-grid-item-base();

      }

      .block:nth-child(3n+1) { /* Span 1 column, starting in the 1st column from left. */

        @include zen-grid-item(1, 1);

        @include zen-clear();

      }

      .block:nth-child(3n+2) { /* Span 1 column, starting in the 2nd column from left. */

        @include zen-grid-item(1, 2);

      }

      .block:nth-child(3n) { /* Span 1 column, starting in the 3rd column from left. */

        @include zen-grid-item(1, 3);

      }

    }

  }

}

@media all and (min-width: 960px) {

  /*

   * Use 5 grid columns for larger screens.

   */

  $zen-column-count: 4;

  /*

   * The layout when there is only one sidebar, the left one.

   */

  .sidebar-first {

    #content { /* Span 4 columns, starting in 2nd column from left. */

      @include zen-grid-item(3, 2);

    }

    .region-sidebar-first { /* Span 1 column, starting in 1st column from left. */

      @include zen-grid-item(1, 1);

    }

  }

  /*

   * The layout when there is only one sidebar, the right one.

   */

  .sidebar-second {

    #content { /* Span 4 columns, starting in 1st column from left. */

      @include zen-grid-item(3, 1);

    }

    .region-sidebar-second { /* Span 1 column, starting in 5th column from left. */

      @include zen-grid-item(1, 4);

    }

  }

  /*

   * The layout when there are two sidebars.

   */

  .two-sidebars {

    #content { /* Span 3 columns, starting in 2nd column from left. */

      @include zen-grid-item(2, 2);

    }

    .region-sidebar-first { /* Span 1 column, starting in 1st column from left. */

      @include zen-grid-item(1, 1);

    }

    .region-sidebar-second { /* Span 1 column, starting in 5th column from left. */

      @include zen-grid-item(1, 4);

    }

  }

}