fix icon

main/template/default/auth/courses_list.php

@@ -17,7 +17,7 @@ $courses_without_category = $courses_in_category[0];
 <!-- Actions: The menu with the different options in cathe course management -->
 <div id="actions" class="actions">
     <?php if ($action != 'subscribe') { ?>
-        &nbsp;<a href="<?php echo api_get_self(); ?>?action=subscribe"><?php echo Display::return_icon('back.png', get_lang('SubscribeToCourse'),'','32'); ?></a>
+        &nbsp;<a href="<?php echo api_get_self(); ?>?action=subscribe"><?php echo Display::return_icon('user_subscribe_course.png', get_lang('SubscribeToCourse'),'','32'); ?></a>
     <?php } ?>
 
     <?php if ($action != 'sortmycourses' && isset($action)) { ?>