Changes url of categories and remove redundant attribute

templates/article.html

@@ -56,7 +56,7 @@
                 {{ article.date.strftime(', %Y') }}    
                 </p>
                 <p>
-                Published by <a href="{{ SITEURL }}/{{ article.author.url }}">{{ article.author }}</a> in <a href="{{ SITEURL }}/categories.html#collapse{{ category|replace(' ', '_')|e }}" "{{ SITEURL }}/{{ article.category.url }}">{{ article.category }}</a> 
+                Published by <a href="{{ SITEURL }}/{{ article.author.url }}">{{ article.author }}</a> in <a href="{{ SITEURL }}/categories.html#{{ category|replace(' ', '-')|e }}-ref">{{ article.category }}</a> 
                 </p>
                 {% if article.modified %} 
                 <p>Updated on {{ article.modified }}

templates/categories.html

@@ -25,7 +25,7 @@ All Categories - {{ super() }}
             {% for category, articles in categories %}
             <div class="accordion-group">
                 <div class="accordion-heading">
-                    <a class="accordion-toggle" data-toggle="collapse" data-parent="#accordion2" href="#collapse{{ category|replace(' ', '_')|e }}">
+                    <a class="accordion-toggle" data-toggle="collapse" data-parent="#accordion2" href="#{{ category|replace(' ', '-')|e }}-ref">
                         {% set num = articles|count %}
                         {{ num }} 
                         {% if num > 1 %}
@@ -36,7 +36,7 @@ All Categories - {{ super() }}
                         filed in {{ category }}
                     </a>
                 </div>
-                <div id="collapse{{ category|replace(' ', '_')|e }}" class="accordion-body collapse">
+                <div id="{{ category|replace(' ', '-')|e }}-ref" class="accordion-body collapse">
                     <div class="accordion-inner">
                         <ul>
                             {% for article in articles %}