Wordpress theme structure

<?php if (have_posts()) : ?>
                <?php while (have_posts()) : the_post(); ?>

                    <div class = "singlecolumnpost">
                        <div <?php post_class() ?>>
                            <?php if (has_post_thumbnail()) : ?>
                                <div class = "post-thumb">
                                    <?php
                                    $next_post = get_next_post();
                                    if (!empty($next_post)):
                                        ?>
                                        <a href="<?php echo get_permalink($next_post->ID); ?>"><?php the_post_thumbnail(); ?></a>
                                    <?php endif; ?>">
                                </div>
                            <?php endif; ?>
                        </div>
                    </div>

                    <div class = "twocolumnpost">
                        <div <?php post_class() ?>>
                            <?php if (has_post_thumbnail()) : ?>
                                <div class = "post-thumb" id = "leftthumb">
                                    <?php
                                    $next_post = get_next_post();
                                    if (!empty($next_post)):
                                        ?>
                                        <a href="<?php echo get_permalink($next_post->ID); ?>"><?php the_post_thumbnail(); ?></a>
                                    <?php endif; ?>">
                                </div>
                            <?php endif; ?>
                        </div>
                        <div <?php post_class() ?>>
                            <?php if (has_post_thumbnail()) : ?>
                                <div class = "post-thumb" id = "rightthumb">
                                    <?php
                                    $next_post = get_next_post();
                                    if (!empty($next_post)):
                                        ?>
                                        <a href="<?php echo get_permalink($next_post->ID); ?>"><?php the_post_thumbnail(); ?></a>
                                    <?php endif; ?>">
                                </div>
                            <?php endif; ?>
                        </div>
                    </div>

                    <div class = "singlecolumnpost">
                        <div <?php post_class() ?>>
                            <?php if (has_post_thumbnail()) : ?>
                                <div class = "post-thumb">
                                    <?php
                                    $next_post = get_next_post();
                                    if (!empty($next_post)):
                                        ?>
                                        <a href="<?php echo get_permalink($next_post->ID); ?>"><?php the_post_thumbnail(); ?></a>
                                    <?php endif; ?>">
                                </div>
                            <?php endif; ?>
                        </div>
                    </div>

                <?php endwhile; ?>