PrimaShop - Create 3 Columns Grid Blog Page

content-featured.php

<?php
/**
 * The template for displaying content using "featured image and excerpt" style. 
 * But we change it to be 3 columns grid.
 *
 * @category PrimaShop
 * @package  Templates
 * @author   PrimaThemes
 * @link     http://www.primathemes.com
 */

if ( ! defined( 'ABSPATH' ) ) exit; // Exit if accessed directly

$prima_column = 3;

// Increase loop count
global $prima_loop;
if ( empty( $prima_loop ) ) 
	$prima_loop = 0;
$prima_loop++;

// Extra post classes
$classes = array();
$classes[] = 'post-blog';
$classes[] = 'post-grid';
if ( 0 == ( $prima_loop - 1 ) % $prima_column || 1 == $prima_column )
	$classes[] = 'first';
if ( 0 == $prima_loop % $prima_column )
	$classes[] = 'last';
	
?>

  <article id="post-<?php the_ID(); ?>" <?php post_class( $classes ); ?> >
	<div class="entry">

	  <h2 class="post-title"><a href="<?php the_permalink(); ?>" title="<?php the_title_attribute(); ?>" rel="bookmark"><?php the_title(); ?></a></h2>
	  
	  <?php echo do_shortcode( prima_get_setting( 'meta_'.get_post_type(), null, '<p class="post-meta"><small>%setting%</small></p>' ) ); ?>

	  <div class="post-content group">
	    <?php prima_image( array ( 'width' => 700, 'height' => 275, 'image_class' => 'image-featured', 'link_to_post' => true ) ); ?>
		<?php the_excerpt(); ?>
	  </div>

	</div>
  </article>

style.css

/* 3 columns blog post grid */
.post-grid {
  margin-right: 3.8%;
  margin-bottom: 25px;
  width: 30.76666667%;
  float: left;
}
.post-grid.first {
  clear:both;
}
.post-grid.last {
  margin-right:0;
}
.post-grid h2.post-title {
  font-size:20px;
}
.navigation {
  clear:both;
}

Tutorial: http://www.primathemes.com/documentation/primashop-create-3-columns-grid-blog-page/