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HTML

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HTML preprocessors can make writing HTML more powerful or convenient. For instance, Markdown is designed to be easier to write and read for text documents and you could write a loop in Pug.

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About the <head>

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CSS

About CSS Preprocessors

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.

Vendor Prefixing

About Vendor Prefixing

To get the best cross-browser support, it is a common practice to apply vendor prefixes to CSS properties and values that require them to work. For instance -webkit- or -moz-.

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JavaScript

About JavaScript Preprocessors

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

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Babel includes JSX processing.

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If the script you link to has the file extension of a preprocessor, we'll attempt to process it before applying.

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Packages

Add Packages

Search for and use JavaScript packages from npm here. By selecting a package, an import statement will be added to the top of the JavaScript editor for this package.

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Using packages here is powered by Skypack, which makes packages from npm not only available on a CDN, but prepares them for native JavaScript ES6 import usage.

All packages are different, so refer to their docs for how they work.

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HTML 

              
                <form>
    <h2>Оформление формы с помощью <span>псевдокласса :placeholder-shown</span></h2>
    <div class="field-group">
        <input type="text" placeholder="Ваше имя" id="name">
        <label for="name">Ваше имя</label>
    </div>

    <div class="field-group">
        <input type="email" placeholder="Email " id="email">
        <label for="email">Email</label>
    </div>

    <div class="field-group">
        <input type="tel" placeholder="Телефон" id="phone">
        <label for="phone">Телефон</label>
    </div>

</form>
!

CSS 

              
                *,
*:before,
*:after {
    box-sizing: border-box;
    font-family: 'Montserrat', sans-serif;
}

body {
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    background: url('https://unsplash.it/1500/1000?image=381');
    background-size: cover;
}

h2 {
    font-size: 18px;
}

h2 span,
a {
    color: #03f;
}

form {
    width: 460px;
    border: 1px solid grey;
    padding: 50px;
    background: white;
    position: relative;
}

form:after {
    content: '';
    display: block;
    width: 104%;
    height: 104%;
    background-image: repeating-linear-gradient(45deg, transparent 10px, transparent 15px, #4E6D7F 15px, #4E6D7F 20px), repeating-linear-gradient(-45deg, transparent 10px, transparent 15px, #4E6D7F 15px, #4E6D7F 20px);
    position: absolute;
    top: -2%;
    left: -2%;
    z-index: -1;
    box-shadow: 0 0 1px 10px rgba(0, 0, 0, 0.1);
}

.field-group {
    position: relative;
}

input {
    font-size: 18px;
    width: 100%;
    padding: 15px;
    margin: 15px 0;
    border: 2px solid #000;
    transition: 0.5s;
}

input + label {
    min-width: 105px;
    text-align: center;
    position: absolute;
    top: 34%;
    left: 70%;
    transition: 0.5s;
    opacity: .6;
    background: white;
    padding: 3px 8px;
}

input:focus {
    outline: 0;
    border-color: #03f;
}

input:focus + label {
    border-color: #03f;
}

input:placeholder-shown + label {
    opacity: 0;
    transform: translate( -100%);
}
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JS
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999px

Console