Add alt attribute to img tags

index.html

@@ -95,7 +95,7 @@ <h4 class="timeline-title">{{ education.organization }}</h4>
                 <h3 class="title with-icon"><span class="fa fa-code cat-title"></span> Programming Skills</h3>
                 {% if site.author.stackoverflow %}
                 <div class="grid-block">
-                  <p><a href="//stackoverflow.com/users/{{ site.author.stackoverflow }}"><img src="//stackoverflow.com/users/flair/{{ site.author.stackoverflow }}.png"></a></p>
+                  <p><a href="//stackoverflow.com/users/{{ site.author.stackoverflow }}"><img alt="stackoverflow-avatar" src="//stackoverflow.com/users/flair/{{ site.author.stackoverflow }}.png"></a></p>
                   <ul class="list-unstyled list-stackoverflow" id="stackoverflow_questions_and_answers"></ul>
                   <script type="text/javascript">
                   $(function () {