$(document).ready(function(){
  var path = window.location.pathname;
  path = path.substring(1);
  var dirs = path.split('/');
  var dir  = dirs[0];
  var a    = $('#gnavi a[href="http://www.web-consultants.jp/'+dir+'/"]');
  a.children('img').attr('src', a.children('img').attr('src').replace('_off2', '_on2') );
});