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HTML

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About the <head>

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CSS

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CSS preprocessors help make authoring CSS easier. All of them offer things like variables and mixins to provide convenient abstractions.

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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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About Vendor Prefixing

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JavaScript

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JavaScript preprocessors can help make authoring JavaScript easier and more convenient.

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Babel includes JSX processing.

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HTML 

              
                <header>
  <div class="header-content">
    
    <a href="#" class="logo">Logo</a>
    
    <input type="checkbox" id="hamburger" aria-label="menu button">
    <label for="hamburger"><span></span></label>
    
    <nav aria-label="main navigation">
      <ul class="menus">
        <li><a href="#">Home</a></li>
        <li>
          <button 
            type="button" 
            aria-haspopup="true" 
            aria-expanded="true" 
            aria-controls="dropdown1"  
          >
            Services<span class="arrow"></span>   
          </button>
          <ul class="dropdown" id="dropdown1">
            <li><a href="#">Web design</a></li> 
            <li><a href="#">Web dev</a></li>
            <li><a href="#">Web</a></li>
          </ul>
        </li>
        <li><a href="#">About</a></li>
      </ul>
    </nav>
  </div>
</header>
!

CSS 

              
                * {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: sans-serif;
}

header {
  position: relative;
  box-shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.07), 0 1px 2px 0 rgba(0, 0, 0, 0.05);
}

.header-content {
  align-items: center;
  max-width: 1200px;
  margin: 0 auto;
  padding: 10px 20px;
  color: #212529;
}

.logo {
  text-decoration: none;
  font-size: 25px;
  color: inherit;
  margin-right: 20px;
}

label {
  padding: 23px 20px;
  position: absolute;
  cursor: pointer;
  right: 0;
  top: 0;
}

input[type="checkbox"] {
  opacity: 0;
  position: absolute;
  right: 0;
}

label span {
  width: 20px;
  height: 3px;
  display: block;
  background: #4f3e3e;
  position: relative;
}

label span::after, label span::before {
  content: "";
  position: absolute;
  display: block;
  background: inherit;
  width: inherit;
  height: inherit;
} 

label span::before{
  top: 8px;
}

label span::after {
  bottom: 8px;
} 

label::before {
  position: absolute;
  content: "";
  width: 58px;
  height: 49px; 
  top: 0;
  right: 0;
}

input[type="checkbox"]:focus + label::before {
  box-shadow: 0 0 20px black;
}

ul {
  background: #f2f2f2;
}

ul li {
   list-style: none;
   font-size: 18px;
}

ul li button {
    font-size: inherit;
    border: none;
    background-color: transparent;
    cursor: pointer;
    width: 100%;
}

ul li a {
   display: block;
   color: inherit;
   text-decoration: none;
}

ul li a, ul li button {
  padding: 0.7rem 1rem;
  text-align: left;
}

.menus {
  position: absolute;
  top: 3.2rem;
  left: 0;
  right: 0;
  
  /*  hide dropdown on small screens  */
  visibility: hidden;
  /*  smooth transitioning  */
  transform: translateY(-1em);
  transition: transform ease 0.2s;
}

/* toggle main dropdown */

input[type="checkbox"]:checked ~ nav > ul {
  visibility: visible;
  transform: translateY(0);
}

.dropdown {
  padding: 2px 1.5rem;
  height: 0;
  overflow: hidden;
  transition: height ease 0.2s;
}

li:focus-within .dropdown {
  height: 135px;
}

.arrow {
  width: 0.5em;
  height: 0.5em;
  display: inline-block;
  vertical-align: middle;
  border-left: 0.15em solid currentColor;
  border-bottom: 0.15em solid currentColor;
  transform: rotate(-45deg);
  margin-left: 0.38em;
  margin-top: -0.25em;
  transition: transform 100ms ease-in-out;
}

li:focus-within > button > .arrow {
  transform: rotate(-225deg);
  margin-top: 4px;
}

/* MEDIA QUERIES  */
@media (min-width: 640px) {
  
  .header-content {
    display: flex;
  }
  
  .menus {
    position: static;
    visibility: visible;
    background: #fff;
    display: flex;
    transform: initial;
  }
  
  label, input[type="checkbox"] {
    display: none;
  }
  
  ul li {
    position: relative;
    font-size: 14px;
  }
  
  ul li a:hover,
  ul li button:hover {
    background-color: #f2f2f2;
  }
  
  .dropdown {
    position: absolute;
    right: 0;
    left: auto;
    box-shadow: 0 10px 15px -3px rgba(46, 41, 51, 0.08),
    0 4px 6px -2px rgba(71, 63, 79, 0.16);
    z-index: 99;
    min-width: 10rem;
    padding: 0;
    background-color: #fff;
    border-radius: 0 0 0.5rem 0.5rem; 
  }
  
  ul li:hover .dropdown {
    height: 135px;
  }
  
  ul li:hover > button > .arrow {
    transform: rotate(-225deg);
    margin-top: 4px;
  }
}
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JS
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