* { box-sizing: border-box;} 
body{font-family:Helvetica,Arial,sans-serif; font-size: 14px;background-image: linear-gradient(to top right, BurlyWood, Cornsilk);} 
div.presentation{width:700px;margin:auto;} 
div.colonne{width: 50%;text-align: center;float: left; background-color:white;
	padding-top:10px}
div.colonne1{width: 50%;text-align: justify;float: left; padding:30px; background-color:white;}
div.colonne2{width: 50%;text-align: justify;float: left; padding:30px;background-color:white;}
div.centrer{width: 100%; text-align: center; padding-left:30px; padding-right:30px; padding-bottom:10px; background-color:white;} b{color:midnightblue;}
a{font-size:18px;} h3.couleur1{color:brown;} h2.couleur2{color:red;}

@media only screen and (max-width:600px){div.presentation{width:100%;} div.colonne{width:100%;} div.colonne1{width:100%;} div.colonne2{width:100%;} div.centrer{width:100%;} img.image{width: 260px; height: 206px;}}