<div class="task_element draggable ui-draggable ui-draggable-handle" id="1_3" data-task-id="36" title="asdfadsf" style="position: relative;"></div>

$('.task_element').click(function(){
   var task_id = $(this).attr('data-task-id');
   window.location.assign('tasks.php?id='+task_id+'');
});