As a user you can make sure that the content of block 2 is less tall than the content of block 3.
For your specific situation there is a stray 5px padding that causes this in your site..
If you go to the file Sources\TPortal.php
find this line:
$context['TPortal']['grid']['rowspan1'][1] = array('before' => '<div class="gridC" style="width:67%;float:left;"><div class="gridColumns" style="width:49%;padding-right: 1%;padding-bottom: 5px;float:left;">', 'after' => '</div>');
and replace this with
$context['TPortal']['grid']['rowspan1'][1] = array('before' => '<div class="gridC" style="width:67%;float:left;"><div class="gridColumns" style="width:49%;padding-right: 1%;float:left;">', 'after' => '</div>');