Mohammad Taqui Sayed

Its because the home page is showing excerpt, and the excerpt filters out iframes and other stuff, You can turn off “show Excerpt” from Supernova Options>Advanced tab and show the whole content.

What embed code did you use ?

Use this css,

.textwidget img{margin: 1px 0;}

1px is the number you would like to adjust

And just noticed the background image you are using is too heave, you should use this image instead.
http://lsp.sjcaalst.be/wp-content/themes/supernova/images/black.png

This error has nothing to do with the theme, looks like there is some plugin which is not compatible yet. Try deactivating each plugin to see which one it is.

Yes it does, you should go ahead and update wordpress.

Well its not that easy, requires some additional coding, I wrote the code for you however i didn’t test that , but I think it should work. If you have a child theme, replace the whole content of includes/index-slider.php with the code below

<?php
/**
 * Template for displaying slider on home page
 *
 * @package Supernova
 * @since Supenova 1.0.4
 * @license GPL 2.0
 */

global $supernova_options, $paged;

$post_ids = get_option('sticky_posts');

if($paged==0 && !supernova_options('disable-slider')): ?>
<div id="supernova_slider_wrapper" class="<?php echo $supernova_options['fade-slider']; ?>">
    <div class="flexslider">
          <ul class="slides">
            <?php
            $post_ids = get_option('sticky_posts');
            if($post_ids){
            foreach($post_ids as $post_id){
                        $slider_image = esc_url(trim($supernova_options['slider'.$i]));
                        $option = $supernova_options['slider-post-excerpt'];
                        $length = $supernova_options['slider-excerpt-length'];
                        $heading_length = $supernova_options['slider-heading-length'];

                    if(!$post_id){ break; } ?>
                <li>
                    <?php if($post_id){ ?>
                        <div class="featured_content">
                               <?php
                               echo     '<a href="'.get_permalink($post_id).'">';
                               echo      "<h3>".supernova_chopper(get_the_title($post_id), $heading_length)."</h3>";
                               if($option != '3'){
                                   if($option == '1'){
                                    echo     "<p>" . get_the_time('F jS, Y', $post_id). "</p>";
                                   }elseif($option == '2'){
                                    echo supernova_get_excerpt_by_id($post_id, $length);
                                   }
                               }
                               echo     '</a>';
                                ?>
                       </div><!--featured content -->
                        <?php }
                                if($slider_image){
                                echo '<img src="'.$slider_image.'" alt="'.get_the_title($post_id).'" />';
                                }else{
                                echo '<img src="'.wp_get_attachment_url(get_post_thumbnail_id($post_id)).'" alt="" />';}
                                ?>
                </li>
           <?php } } //for loop ENDS ?>
          </ul>
    </div> <!--flexslider -->
</div><!--slider_wrapper ENDS -->
<?php endif;

Welcome, your site looks awesome, I didn’t know, someone can make my theme look so good.