title: Jinja doesn't display the background image only for one page
body: <p>I am creating Python/Flask blog and used a Bootstrap template for my front-end. I have a block which remains on each page the same, and the next block(block main) which changes depending on the content. For each of the pages, the background image I set for my static block displays correctly, except one page.</p>
  
  <p>The app structure is the following:
  1. Main page with all the posts/articles
  2. Separate pages for each posts' topic
  3. A page for the specific post which you choose to read about</p>
  
  <p>The issue appears, when I load the page with the post to read it. The background image for the static block disappears.
  When I check the logs, I can see that the code tries to add the link to the background image to the URL of my page and that's why it can't find the picture. How can I make it read my background image link independently of the page URL?</p>
  
  <p><strong>Logs error:</strong>
  <a href="https://i.stack.imgur.com/cXEMS.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/cXEMS.png" alt="enter image description here"></a></p>
  
  <p><strong>HTML</strong></p>
  
  <pre><code>    &lt;header class="masthead" style="background-image:url('static/images/cloud-main.jpg')"&gt;
      &lt;div class="overlay"&gt;&lt;/div&gt;
      &lt;div class="container"&gt;
        &lt;div class="row"&gt;
          &lt;div class="col-lg-8 col-md-10 mx-auto"&gt;
            &lt;div class="site-heading"&gt;
              &lt;h1&gt;Clean Blog&lt;/h1&gt;
              &lt;span class="subheading"&gt;A Blog Theme by Start Bootstrap&lt;/span&gt;
            &lt;/div&gt;
          &lt;/div&gt;
        &lt;/div&gt;
      &lt;/div&gt;
    &lt;/header&gt;
  </code></pre>
  
  <p><strong>Routes</strong></p>
  
  <pre><code>@app.route('/&lt;topic&gt;/&lt;int:post_id&gt;', methods=('GET', 'POST'))
  def post(topic, post_id):
      """
      :param post_id:
      :return: Specific post you clicked in the feed + comments to it
      """
  
      # Retreive the post user clicked at by receiving its id. post_id retrieves from 'history' page
      current_post = models.Post.query.filter_by(post_id=post_id).first()
  
      #Retreive all comments related to the current_post
      comments = current_post.comments
  
      comment_form = forms.NewComment()
  
      if flask.request.method == "POST":
          if comment_form.validate_on_submit():
  
              new_comment = comment_form.get_comment(post_id)
              current_post.add_comment(new_comment)
              flask_login.current_user.add_comment(new_comment)
  
          return flask.redirect(flask.url_for('post', topic=topic, post_id=post_id))
  
      return flask.render_template('post.jin', topic=topic, post=current_post, comments=comments, form=comment_form)
  </code></pre>
  
  <p>I checked this <a href="https://stackoverflow.com/questions/35023107/jinja2-set-background-image">post</a> but it didn't help me. I think the problem is different here.</p>
  
  <p>Thank you!</p>