JSFiddle - React, Tailwind, and code Playground

HTML

<section id="modif"> <a href="#" id="cache">
        <nav>
            <h2>Modifier mon profil</h2>
        </nav>
        </a>

    <nav>
        <form method="post" action="modifications.php" class="modifications">
            <label class="form_col">Modifier mon mot de passe:</label>
            <input type="password" name="modif_pseudo_minecraft" size="30" maxlength="20" />
            <label class="form_col">Modifier adresse e-mail:</label>
            <input type="text" name="email" size="30" />
            <label class="form_col">Modifier date de naissance:</label> <span id="select">
                <select name="jour" id="jour">
                    <option value="1">1</option><option value="2">2</option><option value="3">3</option><option value="4">4</option><option value="5">5</option><option value="6">6</option><option value="7">7</option>
                    <option value="8">8</option><option value="9">9</option><option value="10">10</option><option value="11">11</option><option value="12">12</option><option value="13">13</option><option value="14">14</option>
                    <option value="15">15</option><option value="16">16</option><option value="17">17</option><option value="18">18</option><option value="19">19</option><option value="20">20</option><option value="21">21</option>
                    <option value="22">22</option><option value="23">23</option><option value="24">24</option><option value="25">25</option><option value="26">26</option><option value="27">27</option><option value="28">28</option>
                    <option value="29">29</option><option value="30">30</option><option value="31">31</option>
                </select>
                <select name="mois" id="mois">
                    <option value="Janvier">Janvier</option><option value="Février">Février</option><option value="Mars">Mars</option><option value="Avril">Avril</option><option value="Mai">Mai</option>
                    <option...

CSS

html {
    background-image: url('images/background.jpg');
    font-family: Calibri;
    height: 99%;
}
body {
    margin: 0;
    height: 99%;
}
#modif {
    background-color: rgba(255, 255, 255, 0.7);
    margin-left: auto;
    margin-right: auto;
    width: 40%;
    padding: 20px;
}
a {
    color: black;
    text-decoration: none;
    font-weight: bold;
}
a:hover {
    color: red;
    text-decoration: underline;
}
#formulaire {
    float: left;
    margin-right: 10px;
    padding-bottom: 25px;
    width: 700px;
}
label {
    overflow: auto;
    font-weight: bold;
    display: inline-block;
    margin-left: 40px;
    padding-bottom: 5px;
    padding-top: 5px;
}
input {
    float: right;
    border: 1px black solid;
    box-shadow: 1px 1px 5px black;
    margin-right: 40px;
    padding-top: 5px;
    padding-bottom: 5px;
}
#select {
    float:right;
    margin-right: 40px;
    display: inline-block;
    border-spacing: 10px;
}
#jour {
    float: left;
    border: 1px black solid;
    box-shadow: 1px 1px 5px black;
    margin-left: 172px;
    margin-right: 4px;
    padding-top: 5px;
    padding-bottom: 5px;
}
#mois {
    float: left;
    border: 1px black solid;
    box-shadow: 1px 1px 5px black;
    margin-right: 4px;
    padding-top: 5px;
    padding-bottom: 5px;
}
#annee {
    float: left;
    border: 1px black solid;
    box-shadow: 1px 1px 5px black;
    padding-top: 5px;
    padding-bottom: 5px;
}
#submit {
    float: right;
    border: 1px black solid;
    box-shadow: 1px 1px 5px black;
    background-color: white;
    margin-right: 110px;
    padding-top: 5px;
    padding-bottom: 5px;
}
#submit:hover {
    float: right;
    border: 1px black solid;
    box-shadow: 0 0 0;
    background-color: white;
    margin-right: 110px;
    padding-top: 5px;
    padding-bottom: 5px;
}

JavaScript

$('.modifications').hide();
$('.modifications').css('height', '1000px');
$(function () {
    $('#cache').click(function () {
        $('.modifications').toggle(100);
    });
});