First Header Element Disappears If User Scrolls Down The Page

I have developed the following simple HMTL and CSS code which you can also find in de JSFiddle here: As you can see I have a header consisting of two sub-headers. The .sub-header_

Solution 1:

(function(){
var position = 0; 

  // should start at 0

  $(window).scroll(function() {
      var scroll = $(window).scrollTop();
      if(scroll > position) {
          $('.sub_header_01').hide();
      } else {
          $('.sub_header_01').show();
      }
      position = scroll;
  });
})()

body {
  margin: 0;
}

.header {
  width: 80%;
  height: 10%;
  margin-left: 10%;
  position: fixed;
  top: 0;
  
  box-sizing: border-box;
  border-style: solid;
  border-width: 1px;
  background-color: yellow;
}

.sub_header_01 {
  width: 100%;
  height: 100%;
  float: left;
  text-align: center;
  
  box-sizing: border-box;
  border-style: solid;
  border-width: 1px;
  background-color: blue;   
}

.sub_header_02 {
  width: 100%;
  height: 100%;
  display: flex;
  justify-content: space-between;
  float: left;
  
  box-sizing: border-box;
  border-style: solid;
  border-width: 1px;
  background-color: yellow;
}

.image {
  width: 30%;
  height: 100%;
  
  box-sizing: border-box;
  border-style: solid;
  border-width: 1px;
  background-color: green;
}


/* Navigation */.navigation {
  width: 70%;
  height: 100%;
  position: relative; 
  
  box-sizing: border-box;
  border-style: solid;
  border-width: 1px;
  background-color: aqua;
}

.navigation_button {
 width: 20%;
 height: 100%;
 float: right;
 cursor: pointer;
 
 box-sizing: border-box;
 border-style: solid;
 border-width: 1px;
 background-color: fuchsia;
}

.bar1, .bar2, .bar3 {
 width: 100%;
 height: 20%;
 margin: 4%0;
 background-color: #333; 
}


/* Content */.content {
  width: 80%;
  margin-top: 10%;
  margin-left: 10%;
  box-sizing: border-box;
  border-style: solid;
  border-width: 1px;
  background-color: red;
}

<scriptsrc="https://cdnjs.cloudflare.com/ajax/libs/jquery/2.0.0/jquery.min.js"></script><divclass="header"><divclass="sub_header_01">
  This is a webpage
  </div><divclass="sub_header_02"><divclass="image">
    Image
    </div><divclass="navigation"><divclass="navigation_button"><divclass="bar1"></div><divclass="bar2"></div><divclass="bar3"></div></div></div></div></div><divclass="content"><p>Am no an listening depending up believing. Enough around remove to barton agreed regret in or it. Advantage mr estimable be commanded provision. Year well shot deny shew come now had. Shall downs stand marry taken his for out. Do related mr account brandon an up. Wrong for never ready ham these witty him. Our compass see age uncivil matters weather forbade her minutes. Ready how but truth son new under. Breakfast procuring nay end happiness allowance assurance frankness. Met simplicity nor difficulty unreserved who. Entreaties mr conviction dissimilar me astonished estimating cultivated. On no applauded exquisite my additions. Pronounce add boy estimable nay suspected. You sudden nay elinor thirty esteem temper. Quiet leave shy you gay off asked large style. Betrayed cheerful declared end and. Questions we additions is extremely incommode. Next half add call them eat face. Age lived smile six defer bed their few. Had admitting concluded too behaviour him she. Of death to or to being other. Received shutters expenses ye he pleasant. Drift as blind above at up. No up simple county stairs do should praise as. Drawings sir gay together landlord had law smallest. Formerly welcomed attended declared met say unlocked. Jennings outlived no dwelling denoting in peculiar as he believed. Behaviour excellent middleton be as it curiosity departure ourselves. On then sake home is am leaf. Of suspicion do departure at extremely he believing. Do know said mind do rent they oh hope of. General enquire picture letters garrets on offices of no on. Say one hearing between excited evening all inhabit thought you. Style begin mr heard by in music tried do. To unreserved projection no introduced invitation. Was justice improve age article between. No projection as up preference reasonably delightful celebrated. Preserved and abilities assurance tolerably breakfast use saw. And painted letters forming far village elderly compact. Her rest west each spot his and you knew. Estate gay wooded depart six far her. Of we be have it lose gate bred. Do separate removing or expenses in. Had covered but evident chapter matters anxious. Received overcame oh sensible so at an. Formed do change merely to county it. Am separate contempt domestic to to oh. On relation my so addition branched. Put hearing cottage she norland letters equally prepare too. Replied exposed savings he no viewing as up. Soon body add him hill. No father living really people estate if. Mistake do produce beloved demesne if am pursuit. Cause dried no solid no an small so still widen. Ten weather evident smiling bed against she examine its. Rendered far opinions two yet moderate sex striking. Sufficient motionless compliment by stimulated assistance at. Convinced resolving extensive agreeable in it on as remainder. Cordially say affection met who propriety him. Are man she towards private weather pleased. In more part he lose need so want rank no. At bringing or he sensible pleasure. Prevent he parlors do waiting be females an message society. Situation admitting promotion at or to perceived be. Mr acuteness we as estimable enjoyment up. An held late as felt know. Learn do allow solid to grave. Middleton suspicion age her attention. Chiefly several bed its wishing. Is so moments on chamber pressed to. Doubtful yet way properly answered humanity its desirous. Minuter believe service arrived civilly add all. Acuteness allowance an at eagerness favourite in extensive exquisite ye. Remain valley who mrs uneasy remove wooded him you. Her questions favourite him concealed. We to wife face took he. The taste begin early old why since dried can first. Prepared as or humoured formerly. Evil mrs true get post. Express village evening prudent my as ye hundred forming. Thoughts she why not directly reserved packages you. Winter an silent favour of am tended mutual. </p>

Solution 2:

You can use position:sticky with .sub_header_02 and position:absolute with .sub_header_01 then remove the header wrapper:

body {
  margin: 0;
}

.header {
  
  box-sizing: border-box;
  border-style: solid;
  border-width: 1px;
  background-color: yellow;
}

.sub_header_01 {
  position:absolute;
  top:0;
  height: 10vh;
  width:80%;
  margin:auto;
  left:0;
  right:0;
  text-align: center;
  
  box-sizing: border-box;
  border-style: solid;
  border-width: 1px;
  background-color: blue;   
}

.sub_header_02 {
  height: 10vh;
  width:80%;
  margin:10vh auto 0;
  position:sticky;
  top:0;
  display: flex;
  justify-content: space-between;
  
  box-sizing: border-box;
  border-style: solid;
  border-width: 1px;
  background-color: yellow;
}

.image {
  width: 30%;
  height: 100%;
  
  box-sizing: border-box;
  border-style: solid;
  border-width: 1px;
  background-color: green;
}


/* Navigation */.navigation {
  width: 70%;
  height: 100%;
  position: relative; 
  
  box-sizing: border-box;
  border-style: solid;
  border-width: 1px;
  background-color: aqua;
}

.navigation_button {
 width: 20%;
 height: 100%;
 float: right;
 cursor: pointer;
 
 box-sizing: border-box;
 border-style: solid;
 border-width: 1px;
 background-color: fuchsia;
}

.bar1, .bar2, .bar3 {
 width: 100%;
 height: 20%;
 margin: 4%0;
 background-color: #333; 
}


/* Content */.content {
  width: 80%;
  margin-left: 10%;
  box-sizing: border-box;
  border-style: solid;
  border-width: 1px;
  background-color: red;
}

<divclass="sub_header_01">
  This is a webpage
  </div><divclass="sub_header_02"><divclass="image">
    Image
    </div><divclass="navigation"><divclass="navigation_button"><divclass="bar1"></div><divclass="bar2"></div><divclass="bar3"></div></div></div></div><divclass="content"><p>Am no an listening depending up believing. Enough around remove to barton agreed regret in or it. Advantage mr estimable be commanded provision. Year well shot deny shew come now had. Shall downs stand marry taken his for out. Do related mr account brandon an up. Wrong for never ready ham these witty him. Our compass see age uncivil matters weather forbade her minutes. Ready how but truth son new under. Breakfast procuring nay end happiness allowance assurance frankness. Met simplicity nor difficulty unreserved who. Entreaties mr conviction dissimilar me astonished estimating cultivated. On no applauded exquisite my additions. Pronounce add boy estimable nay suspected. You sudden nay elinor thirty esteem temper. Quiet leave shy you gay off asked large style. Betrayed cheerful declared end and. Questions we additions is extremely incommode. Next half add call them eat face. Age lived smile six defer bed their few. Had admitting concluded too behaviour him she. Of death to or to being other. Received shutters expenses ye he pleasant. Drift as blind above at up. No up simple county stairs do should praise as. Drawings sir gay together landlord had law smallest. Formerly welcomed attended declared met say unlocked. Jennings outlived no dwelling denoting in peculiar as he believed. Behaviour excellent middleton be as it curiosity departure ourselves. On then sake home is am leaf. Of suspicion do departure at extremely he believing. Do know said mind do rent they oh hope of. General enquire picture letters garrets on offices of no on. Say one hearing between excited evening all inhabit thought you. Style begin mr heard by in music tried do. To unreserved projection no introduced invitation. Was justice improve age article between. No projection as up preference reasonably delightful celebrated. Preserved and abilities assurance tolerably breakfast use saw. And painted letters forming far village elderly compact. Her rest west each spot his and you knew. Estate gay wooded depart six far her. Of we be have it lose gate bred. Do separate removing or expenses in. Had covered but evident chapter matters anxious. Received overcame oh sensible so at an. Formed do change merely to county it. Am separate contempt domestic to to oh. On relation my so addition branched. Put hearing cottage she norland letters equally prepare too. Replied exposed savings he no viewing as up. Soon body add him hill. No father living really people estate if. Mistake do produce beloved demesne if am pursuit. Cause dried no solid no an small so still widen. Ten weather evident smiling bed against she examine its. Rendered far opinions two yet moderate sex striking. Sufficient motionless compliment by stimulated assistance at. Convinced resolving extensive agreeable in it on as remainder. Cordially say affection met who propriety him. Are man she towards private weather pleased. In more part he lose need so want rank no. At bringing or he sensible pleasure. Prevent he parlors do waiting be females an message society. Situation admitting promotion at or to perceived be. Mr acuteness we as estimable enjoyment up. An held late as felt know. Learn do allow solid to grave. Middleton suspicion age her attention. Chiefly several bed its wishing. Is so moments on chamber pressed to. Doubtful yet way properly answered humanity its desirous. Minuter believe service arrived civilly add all. Acuteness allowance an at eagerness favourite in extensive exquisite ye. Remain valley who mrs uneasy remove wooded him you. Her questions favourite him concealed. We to wife face took he. The taste begin early old why since dried can first. Prepared as or humoured formerly. Evil mrs true get post. Express village evening prudent my as ye hundred forming. Thoughts she why not directly reserved packages you. Winter an silent favour of am tended mutual. </p>

Solution 3:

I have put something together for you using Javascript.

It's a little more complicated than using pure css but it allows you to see the header no matter how far down the page the user is simply by initiating a scroll up.

// Shadow on Scroll
$(window).scroll(function() {
  var scroll = $(window).scrollTop();
  if (scroll > 0) {
    $('#HeadWrap').addClass('Active');
  } else {
    $('#HeadWrap').removeClass('Active');
  }
  didScroll = true;
});

// Hide header on scroll downvar didScroll,
  lastScrollTop = 0,
  trigger = 0,
  navHeight = $('#HeadWrap').outerHeight();

setInterval(function() {
  if (didScroll) {
    hasScrolled();
    didScroll = false;
  }
}, 0);

functionhasScrolled() {
  var st = $(this).scrollTop();
  // Ensure scroll more than triggerif (Math.abs(lastScrollTop - st) <= trigger)
    return;
  // If past .Head add .NavUp.if (st > lastScrollTop && st > navHeight) {
    // Scroll Down
    $('#HeadWrap').removeClass('NavDown').addClass('NavUp');
  } else {
    // Scroll Upif (st + $(window).height() < $(document).height()) {
      $('#HeadWrap').removeClass('NavUp').addClass('NavDown');
    }
  }
  lastScrollTop = st;
}

html,
body {
  height: 100%;
  margin: 0;
  padding: 0;
}

#HeadWrap {
  position: fixed;
  top: 0;
  width: 100%;
  background: #e5e5e5;
  transition: all .2s ease-in-out;
  z-index: 9999;
}

#HeadWrap.Active {
  box-shadow: 01px3pxrgba(0, 0, 0, 0.5);
}

#HeadWrap.NavUp {
  top: -50px;
}

#Header {
  position: relative;
  height: 50px;
  padding: 010px;
  background: blue;
  color: #fff;
  z-index: 100;
}

#SubHdr {
  background: #111;
  color: #fff;
  display: flex;
  height: 30px;
  white-space: nowrap;
  justify-content: space-between;
}

#Logo {
  background: green;
  width:100px;
}
nav{
  display: flex;
  flex:1;
}
nava{
  display: flex;
  flex:1;
  justify-content:center;
  align-items:center;
  color:#fff;
}
main {
  position: relative;
  padding-top: 90px;
  width: 100%;
  height: 100%;
}

<scriptsrc="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script><divid="HeadWrap"><headerid="Header"class="MxW">
    HEADER
  </header><sectionid="SubHdr"><divid="Logo">
      LOGO
    </div><nav><ahref="#">LINK 1</a><ahref="#">LINK 2</a><ahref="#">LINK 3</a><ahref="#">LINK 4</a><ahref="#">LINK 5</a></nav></section></div><main><p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Ut cursus tellus vitae lacus vestibulum, a consequat metus mattis. Cras viverra mollis finibus. Curabitur maximus purus leo, vitae pellentesque elit consequat at. Sed vestibulum purus fringilla ligula egestas aliquam. Morbi ac euismod neque. Duis egestas magna arcu, vitae porta leo mattis at. Donec non ante ligula. Morbi nec maximus libero. Curabitur euismod efficitur lorem at dignissim. Nulla imperdiet mi a est viverra congue.</p><p>Sed sit amet ornare enim. Sed vestibulum est id ligula auctor lobortis. Vivamus facilisis ligula sed risus laoreet aliquam. Vestibulum cursus accumsan fringilla. Donec consequat massa quis justo tempor malesuada. Quisque elementum viverra lorem, sed vestibulum ipsum efficitur eu. Pellentesque sagittis condimentum justo, eu tristique ante imperdiet et.</p><p>Integer mauris ipsum, dictum sit amet nulla eget, fermentum rhoncus nulla. Mauris id magna mattis, imperdiet est vel, laoreet nisi. Morbi blandit arcu et porttitor condimentum. Morbi lobortis, quam vitae pretium vehicula, nisl magna sagittis nisi, ac pellentesque ligula erat a nunc. Aenean interdum tempus ante in sollicitudin. Aliquam vitae vehicula ligula, bibendum blandit arcu. Integer euismod ullamcorper neque in posuere. Proin sit amet quam neque. Sed bibendum neque ipsum, ut sodales ante aliquet eu. Maecenas ante elit, rutrum eu suscipit at, fringilla eget justo. Cras eu vehicula sapien. Aenean ullamcorper, eros in fermentum tristique, nulla urna lobortis velit, sed semper libero arcu sit amet risus. Nulla luctus imperdiet leo at laoreet. Vivamus luctus ultrices nisi, non sodales mi gravida malesuada.</p>

In hac habitasse platea dictumst. Duis mi nulla, blandit id augue non, imperdiet laoreet odio. Nunc tempor lectus vel tincidunt rutrum. Praesent vel laoreet arcu. Aenean a tincidunt urna. Suspendisse rutrum tempus sem ut egestas. Nam malesuada tellus nibh, eget convallis dolor egestas in. Donec nec accumsan quam. Pellentesque ultrices, ex vel feugiat finibus, ex dui imperdiet elit, eget ultrices sapien tortor dictum lectus. Aliquam sapien metus, faucibus ut elementum euismod, pulvinar sed velit. Ut facilisis fermentum nunc, a sagittis nulla tincidunt in. Ut volutpat facilisis nunc. Aenean nisl nisl, congue nec scelerisque in, euismod vitae libero. Mauris vehicula porta mattis.
</main>