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// ページ内リンクのずれを防ぎます
$('a[href^="#"]').click(function() {
   var speed = 800;
   var adjust = $('.header').height();
   var href= $(this).attr("href");
   var target = $(href == "#" || href == "" ? 'html' : href);
   var position = target.offset().top - adjust;
   $('body,html').animate({scrollTop:position}, speed, 'swing');
   return false;
});