lk_script.js

$('document').ready(function(){
	var sections = $('.slide')
	  , nav = $('#navbar')
	  , nav_height = nav.outerHeight();
	 
	$(window).on('scroll', function () {
	  var cur_pos = $(this).scrollTop();
	 
	  sections.each(function() {
	    var top = $(this).offset().top - nav_height,
	        bottom = top + $(this).outerHeight();
	 
	    if (cur_pos >= top && cur_pos <= bottom) {
	      nav.find('a').removeClass('active');
	      sections.removeClass('active');
	      nav.find('a[href="#'+$(this).attr('id')+'"]').addClass('active');
	    }
	  });
	});

	nav.find('a').on('click', function () {
	  var $el = $(this)
	    , id = $el.attr('href');
	 
	  $('html, body').animate({
	    scrollTop: $(id).offset().top - nav_height + 10
	  }, 500);
	 
	  return false;
	});
});