Вы можете использовать свойство display в CSS
#General {
display: block;
}
.tabcontent{
display: none;
}
Также добавьте активный класс на первую кнопку (General) .. чтобы вы увидели кнопку General в белом (как выбрано) ..
<button class="tablinks active" onclick="openTab(event, 'General')">Général</button>
function openTab(evt, tab) {
// Declare all variables
var i, tabcontent, tablinks;
// Get all elements with class="tabcontent" and hide them
tabcontent = document.getElementsByClassName("tabcontent");
for (i = 0; i < tabcontent.length; i++) {
tabcontent[i].style.display = "none";
}
// Get all elements with class="tablinks" and remove the class "active"
tablinks = document.getElementsByClassName("tablinks");
for (i = 0; i < tablinks.length; i++) {
tablinks[i].className = tablinks[i].className.replace(" active", "");
}
// Show the current tab, and add an "active" class to the link that opened the tab
document.getElementById(tab).style.display = "block";
if(evt){
evt.currentTarget.className += " active";
}
}
html, body{
margin: 0;
padding: 0;
top: 0;
}
#sidebar{
background: #c5deea;
background: -moz-linear-gradient(top, #c5deea 0%, #8abbd7 31%, #066dab 100%);
background: -webkit-linear-gradient(top, #c5deea 0%,#8abbd7 31%,#066dab 100%);
background: linear-gradient(to bottom, #c5deea 0%,#8abbd7 31%,#066dab 100%);
filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#c5deea', endColorstr='#066dab',GradientType=0 );
position: fixed;
z-index: 1;
top: 0;
left: 0;
top: 0;
height:100%;
width:20%;
}
#photo{
width:100%;
height:40%;
}
.sidenav button {
width: 100%;
height: 75px;
padding: 6px 8px 6px 16px;
font-family: sans-serif;
font-size: 25px;
text-decoration: none;
text-align: center;
color: darkslategrey;
background-color: transparent;
border: none;
outline: none;
display: block;
}
.sidenav button:hover {
background-color: navajowhite;
}
.sidenav button.active {
background-color: white;
}
.tabcontent{
background: transparent;
position: fixed;
z-index: 1;
top: 0;
left: 20%;
top: 0;
padding: 2.5%;
height:97.5%;
width:75%;
}
h3{
font-family: sans-serif;
}
table {
border-collapse: collapse;
border-spacing: 0;
width: 100%;
border: 1px solid #ddd;
border-radius: 25px;
font-family: sans-serif;
}
th, td {
text-align: left;
padding: 16px;
}
.bold {
background-color:antiquewhite;
font-weight: bold;
}
#General {
display: block;
}
.tabcontent{
display: none;
}
.container {
width: 100%; /* Full width */
background-color: #ddd; /* Grey background */
}
.skills {
text-align: right; /* Right-align text */
padding: 10px; /* Add some padding */
color: white; /* White text color */
}
.html {width: 90%; background-color: #4CAF50;} /* Green */
.css {width: 80%; background-color: #2196F3;} /* Blue */
.js {width: 65%; background-color: #f44336;} /* Red */
.php {width: 60%; background-color: #808080;} /* Dark Grey */
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta charset="utf-8" />
<title>My CV online</title>
<link href="style.css" rel="stylesheet" />
</head>
<body>
<div id="sidebar">
<div id="photo">
<img src="https://raw.githubusercontent.com/DevFrancoisXavierPelletier/CV/master/image.png" alt="Francois Xavier Pelletier" style="width:75%;height:75%; padding: 12.5%;">
</div>
<div class="sidenav">
<button class="tablinks active" onclick="openTab(event, 'General')">Général</button>
<button class="tablinks" onclick="openTab(event, 'Experience')">Expérience</button>
<button class="tablinks" onclick="openTab(event, 'Studies')">Etudes</button>
<button class="tablinks" onclick="openTab(event, 'Skills')">Compétences</button>
</div>
</div>
<div id="General" class="tabcontent">
<h3>Informations générales</h3>
<table class="table">
<tr>
<td class="bold">Prénom</td>
<td class="bold">Nom</td>
<td class="bold">Age</td>
</tr>
<tr>
<td>François Xavier</td>
<td>Pelletier</td>
<td>29 ans</td>
</tr>
<tr>
<td class="bold">Adresse</td>
<td class="bold">Code Postal</td>
<td class="bold">Ville</td>
</tr>
<tr>
<td>52 rue Madame de Maintenon</td>
<td>78120</td>
<td>Rambouillet</td>
</tr>
</table>
<h3>Contact</h3>
<table class="table">
<tr>
<td class="bold">Téléphone</td>
<td class="bold">Email</td>
</tr>
<tr>
<td>+33 **********</td>
<td>dev.francois.xavier.pelletier@gmail.com</td>
</tr>
</table>
<h3>Mobilité</h3>
<table class="table">
<tr>
<td class="bold">Permis</td>
<td class="bold">Véhicule</td>
</tr>
<tr>
<td>B</td>
<td>Non</td>
</tr>
</table>
</div>
<div id="Experience" class="tabcontent">
<h3>Experience</h3>
<table class="table">
<tr>
<td class="bold">Nom du projet</td>
<td class="bold">Adresse en ligne</td>
<td class="bold">Contact</td>
</tr>
<tr>
<td>Eagle-dev</td>
<td>www.eagle-dev.com</td>
<td>dev.francois.xavier.pelletier@gmail.com</td>
</tr>
<tr>
<td></td>
<td></td>
<td></td>
</tr>
</table>
</div>
<div id="Studies" class="tabcontent">
<h3>Etudes</h3>
<table class="table">
<tr>
<td class="bold">Année</td>
<td class="bold">Nom de l'établissement</td>
<td class="bold">Statut</td>
</tr>
<tr>
<td>2018-2019</td>
<td>IFOCOP (Paris) - Développeur intégrateur web</td>
<td>En cours</td>
</tr>
<tr>
<td>2014-2017</td>
<td>War Studies Academy (Varsovie) - Relations internationales</td>
<td>Licence obtenue</td>
</tr>
</table>
</div>
<div id="Skills" class="tabcontent">
<h3>Compétences</h3>
<p>HTML</p>
<div class="container">
<div class="skills html">90%</div>
</div>
<p>CSS</p>
<div class="container">
<div class="skills css">80%</div>
</div>
<p>JavaScript</p>
<div class="container">
<div class="skills js">40%</div>
</div>
<p>PHP</p>
<div class="container">
<div class="skills php">0%</div>
</div>
</div>
<script src="myScript1.js"></script>
</body>