body {
  background: white;
  margin-left: 7%;
  margin-right: 7%;
  font-family: sans-serif;
}

h1,h2,h3,h4,h5,h6 { 
  margin-left: -3%;
}

div.form { 
  background: rgb(204,204,255);
  padding: 1em;
  border: none;
  margin-left: 10%;
  margin-right: 10%;
}

a:hover{ 
  color: blue;
  background-color: yellow;
 }

.cadre { 
  border: solid;
  border-width: thin;
  }