#slider {
width: 80% max-width: 1000px;}
#slider figure {
position relative;
width: 500%;
margin: 0;
padding: 0;
font-size: 0;
text-align: center;
}
# slider figure img {
width: 20%;
height: auto;
float: left;
}
#slider { 
width: 80%;
max-width: 500px;
overflow: hidden;
animation-timing-function: ease-in-out;
}
@keyframes slidy {
0% { left: 0%; }
20% { left: 0%; }
25% { left: -100%; }
45% { left: -100%; }
50% { left: -200%; }
70% { left: -200%; }
75% { left: -300%; }
95% { left: -300%; }
100% { left: -400%; }
}
#slider figure {
position: relative;
width: 500%;
margin: 0;
padding: 0;
font-size: 0;
left: 0;
text-align: left;
animation: 10s slidy infinite;
}
.pagination-container {
text-align: center;
}

.pagination {
  display: inline-block;
margin: 0;
}

.pagination a {
  color: black;
  float: left;
  padding: 7px 14px;
  text-decoration: none;
  transition: background-color .3s;
  border: 1px solid #ddd;
 }
.pagination li {
display: inline;
}

.pagination a.active {
  background-color: #4CAF50;
  color: white;
  border: 1px solid #4CAF50;
}
.pagination a:hover:not(.active) {background-color: #ddd;}

.liste {
 font-size: 1.5em;
 font-family: Harrington;
 border-style: none;
 color: #2f5f9f;
 font-weight: normal;
}
.button1 {
  background-color: black;
  border: none;
  color: white;
  padding: 15px 32px;
  text-align: center;
  text-decoration: none;
  display: inline-block;
  font-size: 16px;
  margin: 4px 2px;
  cursor: pointer;
}
.newspaper {
  column-count: 3;
}
#navbar {
padding-left: 5px;
background-color: #2f5f9f;
text-align: center;
padding-top: 10px;
padding-bottom: 10px;
color: white;
}
#navbar li {
display: inline;
list-style: none;}
#navbar a {
display: inline-block;
text-decoration: none;
min-width: 120px;
text-align: center;
margin: 0.5rem;
padding: 0.4rem 0;
border: 1px solid #ffff;
border-radius: 4px;
}
body {
margin: 0 auto;
border: 2px dotted #2f5f9f;
font-family: Verdana, Arial;
margin: 0px auto;
min-width: 320px;
max-width: 870px;
margin: 0 auto;
width: 100%;
 background-image :url(fond0.JPG);
  }
.content {
line-height: 1em;
font-style: normal;
font-weight: normal;
width: 100%;
font-style: normal;
font-weight: normal;
font-size: 1em;
font-family: verdana;
display: block;
text-align: left;
background-color:white;
color: grey;
}
a:link {
  border-style: none;
  font-style: normal;
text-decoration: none;
  font-size: 0.9em;
  text-align: left;
  font-weight: normal;
  text-transform: uppercase;
  line-height: 1.5em;
  color: #ff9966;

}
a:visited {
  border-style: none;
  font-family: Verdana;
  font-size: 1em;
  line-height: 1em;
  font-weight: normal;
  font-style: normal;
  text-align: left;
  text-transform: capitalize;
  text-decoration: none;
  color: #66cccc;
}
a:active {
  border-style: none;
  font-family: Verdana;
  font-size: 1em;
  line-height: 1em;
  font-weight: normal;
  font-style: normal;
  text-transform: uppercase;
  text-decoration: none;
  text-align: left;
  color: #ff9999; 
}
.video-conteneur iframe,
.video-conteneur object,
.video-conteneur embed {
position:absolute;
top:0;
left:0;
width:100%;
height:auto;
}
.footer {
  margin: 0 auto;
  max-width: 100%;
  font-weight: normal;
  text-decoration: none;
  text-transform: uppercase;
  font-family: Verdana;
  font-size: 0.9em;
  line-height: 0.9em;
  font-style: normal;
  text-align: center;
  color: white;
  clear: both;
  background-color: #2f5f9f;
  padding-top: 10px;
  padding-bottom: 10px;
  height: 50px;
}
h1 {
  font-family: Great Victorian; 
  line-height: 1em;
  text-transform: none;
  text-align: left;
  color: black;
  font-size: 2.5em;
}
h2 {
  text-decoration: none;
  font-style: normal;
  line-height: 1em;
  font-weight: normal;
  font-family: Gabriola;
  color: #2f5f9f;
  font-size: 2em;
  text-align: center;
  text-transform: none;
 }
h3 {
  line-height: 1em;
  text-decoration: none;
  font-style: normal;
  color: #3d7acc;
  font-family: Harrington;
  text-transform: capitalize;
  font-weight: bold;
  text-align: center;
  font-size: 1.5em;
}
.container {
    display: flex;
    padding: 0px;
    flex-wrap: wrap;
    justify-content: center;
    align-items: column; 
  }
  .card {
   padding: 10px;
    flex: 0 0 200px;
    margin: 10px;
    background: white;
    border: 1px solid #ccc;
    box-shadow: 2px 2px 6px 0px  rgba(0,0,0,0.3);

  } 
  .card img {
   padding: 0px;
    max-width: 100%;
  }
  .card .text {
    padding: 0 20px 20px;
  }
  .card .text > button {
    background: gray;
    border: 0;
    color: white;
    padding: 10px;
    width: 100%;
    }
.button {
    background: gray;
    border: 1px solid gray;
    color: white;
    padding: 10px;
    width: 100%;
    }
.button:hover {
    background: #ebebeb;
    color: black;
border: 1px solid black;
}

.header {
 background-color: white;
text-align: center;
 <img src="blog.JPG"
 alt="logo de mon site>
}

.header h1 {
    font-size: 50px;
    text-align: center;
 color: #2f5f9f;
}
.header p {
    font-size: 30px;
    text-align: left;  
}
.footer a {
color: white;
}
p{
font-size: 0.9em;
line-height: 1em;
text-align: left;
color: #2f5f9f;
padding:10px;
margin:30px;
 }
}
.miseEvidence {
  border-style: none;
  font-style: normal;
  font-weight: normal;
  color: #af4520;
  text-transform: uppercase;
  font-size: 1em;
  line-height: 1em;
  text-decoration: none;
  font-family: Verdana;
  text-align: justify;
}
.first-letter {
  border-style: none;
  font-size: 1.2em;
  font-weight: normal;
  font-style: normal;
  text-transform: none;
  text-decoration: none;
  line-height: 1em;
  text-align: center;
  color: #596e84;
}
.first-line {
  border-style: none;
  text-indent: 20px;
  font-variant: small-caps;
  text-align: center;
  text-decoration: none;
  line-height: 1em;
  text-transform: uppercase;
  font-size: 14px;
  font-family: Verdana;
  color: #646c55;
  font-weight: lighter;
  font-style: italic;
}
{
position:relative;
padding-bottom:56.25%;
height:0;
overflow:hidden;
}
 
.video-conteneur iframe,
.video-conteneur object,
.video-conteneur embed {
position:absolute;
top:0;
left:0;
width:100%;
height:100%;
}


@media (max-width: 640px) {
	* {
		box-sizing: border-box;
	}
	
	/* passer body (et tous les  l ments de largeur fixe) en largeur automatique */

	body {
		width: auto;
		margin: 0;
		padding: 0;
	}
	
	/* fixer une largeur maximale de 100% aux  l ments potentiellement probl matiques */

	img,
	table,
	td,
	blockquote,
	code,
	pre,
	textarea,
	input,
	iframe,
	object,
	embed,
	video {
		max-width: 100%;
	}
	
	/* conserver le ratio des images */

	img {
		height: auto;
	}
	
	/* gestion des mots longs */

	textarea,
	table,
	td,
	th,
	code,
	pre,
	samp {
		-webkit-hyphens: auto; /* c sure propre */
		-moz-hyphens: auto;
		hyphens: auto;
		word-wrap: break-word; /* passage   la ligne forc  */
	}
	
	code,
	pre,
	samp {
		white-space: pre-wrap; /* passage   la ligne sp cifique pour les  l ments   ch sse fixe */
	}
	
	/* Passer   une seule colonne (  appliquer aux  l ments multi-colonnes) */

	.element1,
	.element2 {
		float: none;
		width: auto;
	}
	
	/* masquer les  l ments superflus */

	.hide_mobile {
		display: none !important;
	}
	


	


La touche finale : r duire de fa on harmonieuse toutes les tailles de polices en orientation paysage (car buggu e sur les p riph riques iPhone et iPad).

@media (max-device-width:768px) and (orientation: landscape) {
  html {
   -webkit-text-size-adjust: 100%;
   -ms-text-size-adjust: 100%;
  }
} 

{
position:relative;
padding-bottom:56.25%;
height:0;
overflow:hidden;
}