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About the <head>

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CSS

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CSS Base

About CSS Base

It's a common practice to apply CSS to a page that styles elements such that they are consistent across all browsers. We offer two of the most popular choices: normalize.css and a reset. Or, choose Neither and nothing will be applied.

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JavaScript

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Babel includes JSX processing.

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HTML 

              
                <div class="scrollcounter"> 0px</div>
<div class="header"><h1>I am a title</h1></div>
<div class="container">
<div class="row">
<div class="col-md-12 content">
  <a href="http://www.skippyweb.nl/2017/02/19/animate-page-based-on-the-users-scroll-position/" target="_blank">There scripts belong to a blogpost on Skippy Web</a><Br>
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Reprehenderit nemo nulla provident perspiciatis eos molestias consequuntur reiciendis unde, ipsum excepturi quia maxime voluptatibus hic, quod veniam in.Lorem ipsum dolor sit amet, consectetur adipisicing elit. Soluta quibusdam ut, dolorem tenetur suscipit, dolores eius dignissimos explicabo atque consectetur, et debitis quam eum necessitatibus, nisi veritatis inventore cupiditate natus.Lorem ipsum dolor sit amet, consectetur adipisicing elit. At laboriosam, maiores veritatis quos sunt officia vitae nemo. Voluptate, quae ducimus error ullam natus quas est tenetur cupiditate perferendis tempora? Vero?Lorem ipsum dolor sit amet, consectetur adipisicing elit. Blanditiis iusto, voluptatibus quasi consequuntur minus, sequi quidem, magnam, animi unde architecto natus. Doloribus possimus iste in expedita quae, blanditiis consectetur aspernatur.Lorem ipsum dolor sit amet, consectetur adipisicing elit. Qui non eveniet impedit repellendus voluptas! 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Veniam iure, aliquam nesciunt vel recusandae velit beatae saepe, explicabo facere sit omnis minus excepturi qui natus nihil vero quis. Iure, assumenda.Lorem ipsum dolor sit amet, consectetur adipisicing elit. Consequuntur esse vero possimus delectus culpa dolorum sit fugiat architecto beatae similique eos voluptas numquam, recusandae repudiandae incidunt in fugit temporibus nobis.Lorem ipsum dolor sit Lorem ipsum dolor sit amet, consectetur adipisicing elit. Ea eaque laudantium laborum fuga minus! Error laborum asperiores laboriosam expedita officia modi debitis tenetur, dicta at nesciunt consectetur. Tenetur, quaerat commodi!Lorem ipsum dolor sit amet, consectetur adipisicing elit. Velit, natus! Expedita nisi unde, officiis provident assumenda suscipit excepturi, quibusdam possimus doloremque delectus numquam sunt repudiandae asperiores obcaecati quidem eaque dolorum?Lorem ipsum dolor sit amet, consectetur adipisicing elit. 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Dignissimos praesentium, reprehenderit excepturi quia vero tempora illo dolores, obcaecati dolorum magni earum reiciendis inventore nemo iure a harum, hic itaque exercitationem.</div>
!

CSS 

              
                .header{
  height: 250px;
  width: 100%;
  top:0;
  left: 0;
  right: 0;
  position: fixed;
  z-index: 1;
  background-image: url(https://www.skippyweb.nl/wp-content/uploads/2017/02/pexels-photo-220144.jpeg);
  background-repeat: no-repeat;
  background-position:center center; 
  background-attachment: fixed;
  background-size: cover;
  transition-duration: 0.5s;

}
.header h1{
  font-size: 50px;
  
  color: #fff;
  position: absolute;
  top:50%;
  margin: -30px 0 0 0;
  left:0;
  right:0;
  text-align: center;
}
.header.slim{
  height: 70px;
}
.content{
  width: 1200px;
  margin: 300px auto 0 auto;
  font-size: 15px;
  line-height: 18px;
}
.scrollcounter{
  position: fixed;
  top:0;
  right:0;
  background: red;
  padding: 10px;
  color: #fff;
  z-index: 999;
}
!

JS 

              
                  $(window).scroll(function(event) {
    var scrolledValue = $(window).scrollTop();
    var topElem = $('.header');
    $('.scrollcounter').empty().append(scrolledValue+"px");

    
     if(scrolledValue >= 50){
       topElem.addClass('slim');
     }else{
       topElem.removeClass('slim');
     }
  });
!
999px

Console