Horizontal timeline while descending the page

(function($){
	$(function(){
	  
	  // Slider functionality
	  
	    // slide knob to position function
	    (function( $ ){
         $.fn.slideToPos = function() {
           var left = $(this).position().left + ($(this).width() / 2) - ($(".menu a.knob").width() / 2) - 2;
           $(".menu a.knob").css("left", left);
           var before = $(this).parent().parent().parent().children(".bar").first().children(".before").first();
           before.css("width", left + 20).css("backgroundColor", $($(this).attr("href")).css("backgroundColor"));
           return this;
         }; 
      })( jQuery );
	 	  
	 	$(".menu ul li.active a").slideToPos();     
    $(".menu ul li a").click(function(e) {
      e.preventDefault();
      $(this).slideToPos();
      $('html, body').animate({ scrollTop: $(this.hash).offset().top }, 400);
    });
    
    
    // Scroll Spy
    $(window).scroll(function() {
      var top = $(window).scrollTop() + 100; // Take into account height of fixed menu
      $(".container").each(function() {
        var c_top = $(this).offset().top;
        var c_bot = c_top + $(this).height();
        var hash = $(this).attr("id");
        var li_tag = $('a[href$="' + hash + '"]').parent();
        if ((top > c_top) && (top < c_bot)) {
          
          if (li_tag.hasClass("active")) {
            return false;
          }
          else {
            li_tag.siblings().andSelf().removeClass("active");
            li_tag.addClass("active");
            $(".menu ul li.active a").slideToPos();  
        	}
        }
      });
    });
	
	}); // end of document ready
})(jQuery); // end of jQuery name space

html, body, div, span, applet, object, iframe,
h1, h2, h3, h4, h5, h6, p, blockquote, pre,
a, abbr, acronym, address, big, cite, code,
del, dfn, em, img, ins, kbd, q, s, samp,
small, strike, strong, sub, sup, tt, var,
b, u, i, center,
dl, dt, dd, ol, ul, li,
fieldset, form, label, legend,
table, caption, tbody, tfoot, thead, tr, th, td,
article, aside, canvas, details, embed, 
figure, figcaption, footer, header, hgroup, 
menu, nav, output, ruby, section, summary,
time, mark, audio, video {
	margin: 0;
	padding: 0;
	border: 0;
	font-size: 100%;
	font: inherit;
	vertical-align: baseline;
}
/* HTML5 display-role reset for older browsers */
article, aside, details, figcaption, figure, 
footer, header, hgroup, menu, nav, section {
	display: block;
}
body {
	line-height: 1;
}
ol, ul {
	list-style: none;
}
blockquote, q {
	quotes: none;
}
blockquote:before, blockquote:after,
q:before, q:after {
	content: '';
	content: none;
}
table {
	border-collapse: collapse;
	border-spacing: 0;
}

/* CSS RESET DONE */

html,body { height: 100%; }
body {
  color: #fff;
  margin: 0 auto;
  font: 1em/1.3em Helvetica, sans-serif;
	background-color: #333;  
}
.header {
  margin-bottom: 40px;
}
.clearfix {
  clear: both;
}

.container {
  z-index: 1;
  position: relative;
  background-color: #f4d432;
  padding-top: 120px;
  text-align: center;
  height: 100%;
}
  .container.blue {
    background-color: #0099cc;
  }
  .container.green {
    background-color: #9ed846;
  }
  .container.red {
    background-color: #ff6766;
  }


h1 {
  margin: 40px 0;
  font-size: 40px;
  line-height: 40px;
  font-weight: bold;
  text-shadow: 0px 1px 1px #888;
}
a {
  text-decoration: none;
  color: #fff;  
  margin: 0 10px;
}

.btn {
  box-sizing:border-box;
   -moz-box-sizing:border-box;
   -webkit-box-sizing:border-box;
  
  position: relative;
  display: inline-block;
  padding: 10px 20px;
  height: 50px;
  background-color: #666;
  
  border-radius: 30px;
  -moz-border-radius: 30px;
  -webkit-border-radius: 30px;
  
  line-height: 30px;
  font-size: 16px;
  font-weight: bold;
  text-shadow: 0px 1px 1px #888;
}
  a.btn span.btn {
    position: absolute;
    top: 4px;
    left: 0;
    z-index: -1;
    
    width: 100%;
    background-color: #444;
  }
  .btn:active,
  .btn:active > span.btn{
    top: 2px;
  }
  .btn.active,
  .btn.active > span.btn {
    top: 2px;
  }
.btn-small {
  height: 30px;
  font-size: 12px;
  line-height: 10px;
}
  a.btn-small span.btn {
    height: 30px;
  }


/* Menu Styles */

.menu {
  width: 100%;
  position: fixed;
  height: 100px;
  background-color: #fff;
  top: 0;
  left: 0;
  z-index: 2;
}
  .menu .slider {
    position: relative;
    left: 10%;
    width: 80%;
    text-align: center;
  }
  
    .menu .slider .bar, .menu .slider .bar .before {
      height: 20px;
 
      transition: .5s; 
      -webkit-transition: .5s; 
     
      border-radius: 20px;
      -moz-border-radius: 20px;
      -webkit-border-radius: 20px;
    }
    
    .menu .slider .bar {
      position: relative;
      left: 3px;
      width: 100%;
      background-color: #777;
    }
      .menu .slider .bar .before {
        width: 100px;
        float: left;
        position: relative;
        left: -3px;
      }
      .menu .slider .bar a.knob { 
        position: absolute;
        top: -5px;
        left: 0;
        margin: 0;
        display: block;
        width: 30px;
        height: 30px;
        background-color: #ccc;

        border-radius: 15px;
        -moz-border-radius: 15px;
        -webkit-border-radius: 15px;
        
        transition: .5s; 
        -webkit-transition: .5s; 
      }
    .menu ul { 
      height: 100%; 
      display: inline-block;
      margin: 20px 0 15px 0;
    }
    .menu ul li {
      margin: 0 40px;
      font-size: 12px;
      font-weight: bold;
      float: left;
    }
    .menu ul li a { color: #444; margin: 0; }
    

<!DOCTYPE html>
<head>
  <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
  <title>Slider Timeline Menu</title>
  <link href="style.css" type="text/css" rel="stylesheet" media="screen,projection" />
  <link href="http://netdna.bootstrapcdn.com/font-awesome/3.2.1/css/font-awesome.css" rel="stylesheet">
</head>

<body>
    <div class="menu">
      <div class="slider">
        <ul>
          <li class="category active"><a href="#home">HOME</a></li>
          <li class="category"><a href="#search">SEARCH</a></li>
          <li class="category"><a href="#about">ABOUT US</a></li>
          <li class="category"><a href="#contact">CONTACT US</a></li>
        </ul>
        <div class="bar">
          <div class="before"></div>
          <a class="knob"></a>
          <div class="after"></div>
        </div>
      </div>
    </div>
    
    <div id="home" class="container">
      <div class="header">
        <a href="http://webdesigncrowd.com" class="btn">WebDesignCrowd <span class="btn"></span></a>
        <a href="http://www.webdesigncrowd.com/css3-slider-timeline-menu/" class="btn">Back to Article <span class="btn"></span></a>
        <h1>Slider Timeline Menu</h1>
      </div>
    </div>
    <div id="search" class="container blue">
      <h1>Search</h1>
    </div>
    <div id="about" class="container green">
      <h1>About Us</h1>
    </div>
    <div id="contact" class="container red">
      <h1>Contact Us</h1>
    </div>
    
  
  <!-- Javascript -->
  <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script><scriptsrc="js/init.js"></script>
</body>
</html>