AddThis

Twitter Follow Button Not Working

Every other button connects properly except for Twitter. Here is the code:

<!-- AddThis Follow BEGIN -->
<p>Follow Me</p>
<div class="addthis_toolbox addthis_32x32_style addthis_vertical_style">
<a class="addthis_button_facebook_follow" addthis:userid="krmarks"></a>
<a class="addthis_button_twitter_follow" addthis:userid="marksology"></a>
<a class="addthis_button_linkedin_follow" addthis:userid="kennethrmarks"></a>
<a class="addthis_button_google_follow" addthis:userid="111400982461896544577"></a>
<a class="addthis_button_pinterest_follow" addthis:userid="kenmarksology"></a>
<a class="addthis_button_tumblr_follow" addthis:userid="marksology"></a>
</div>
<script type="text/javascript" src="http://s7.addthis.com/js/250/addthis_widget.js#pubid=xa-500067a82447d765"></script>
<!-- AddThis Follow END -->

The site it is on is http://marksology.weebly.com/index.html

Please let me know what I did wrong,

Thanks