.btn { border: none; background-color: inherit; padding: 5px 0px; font-size: 18px; cursor: pointer; display: inline-block; color: darkblue;}
.btn:hover {color: red;}
.a:hover {color: red;}
div{padding:2px;}
* { box-sizing: border-box;} 
body{text-align:center;font-family:Helvetica,Arial,sans-serif; font-size: 14px;background-image: linear-gradient(to top right, BurlyWood, Cornsilk);}
#presentation{background-image: url("fond_rosenquist.png");width:690px; height: 864px; padding-top:60px; background-color:white;margin:auto;} 
div.droite1{text-align:right; padding-top:30px; padding-right:5px; }
a{font-size:18px;}
b.couleur1{color:brown;font-size:20px;} 
h1.couleur2{color:blue;}
u.bleu {font-size:18px;}
@media only screen and (max-width:600px){#presentation{width:100%; background-image: linear-gradient(to bottom left, rgb(153, 230, 153), Linen); } #fenetre{width:100%;} }