<?php
/**
 * @file
 * Returns the HTML for a block.
 *
 * Complete documentation for this file is available online.
 * @see https://drupal.org/node/1728246
 */
?>

<div id="<?php print $block_html_id; ?>" class="<?php print $classes; ?>"<?php print $attributes; ?>>

  <?php print render($title_prefix); ?>
  <?php if (isset($title) && !empty($title)): ?>
    <h1<?php print $title_attributes; ?>><?php print $title; ?></h1>
  <?php endif; ?>
  <?php print render($title_suffix); ?>

  <div class="block__content">
    <?php print $content; ?>
  </div>

</div>

Create block template so that blocks in left siderbar will use <h1> element for block title (accessibility issue).
Create block template so that blocks in left siderbar will use <h1> element for block title (accessibility issue).
