$(function(){

  $('.next_section').click(function()
      {
       var t = $(this);
       var section_div = t.parent('.section_div').next('.section_div');
       var hash =section_div.attr('id');
       window.location.hash = '#'+hash;
       
      });
  $('.prev_section').click(function()
      {
       var t = $(this);
       var section_div = t.parent('.section_div').prev('.section_div');
       var hash =section_div.attr('id');
       window.location.hash = '#'+hash;
       
      });

    
             });