Asa ar trebui sa fie OK.

Cod:
    <article id="post-<?php the_ID(); ?>" <?php post_class("archive artmain col-md-4 col-sm-8 col-xs-12"); ?>>
       
        <div class="main-article curb-effect">  
            <div class="feat-thumb-holder">
               
                <?php if (has_post_thumbnail()) { ?>   
                        <a href="<?php the_permalink(); ?>" title="<?php the_title_attribute(); ?>"><?php the_post_thumbnail('grid-thumb'); ?></a>   
                <?php } else { ?>
                        <a href="<?php the_permalink(); ?>" title="<?php the_title_attribute(); ?>"><img width=330 height=270 src="<?php echo get_template_directory_uri()."/images/cthumb.png" ?>"></a>
                <?php } ?> 

            </div>
        </div>
        <h2 class="main-entry-title"><a href="<?php the_permalink(); ?>" rel="bookmark"><?php the_title(); ?></a></h2>
    </article><!-- #post-## -->