* {box-sizing: border-box}

a {
  text-decoration: none;
  color: #0D47A1;  
}
a:hover { 
  color: #BF360C; 
}

html {
  position: relative;
  min-height: 100%;
}
p {
 font-size: 1.3rem;
 margin-top: .5rem;  
 margin-bottom: .5rem;
}

.petit {
 font-size: 1em;
}
.titre1 {
 font-size: 1.3rem;
 font-weight: bolder; 
 color: darkgreen;
 text-align: center;
 margin-top: .8rem; 
 margin-bottom: .8rem;
}
.preface {
 font-size: 1.3rem;
 font-style: italic;
 color: brown;
 text-align: left;
 margin-top: .5rem; 
 margin-bottom: .5rem;
} 

header {
  background: #B2DFDB;
  font-size: 1.4rem;  
  height: auto;
  text-align: center;
  color: darkgreen;
  border-color: darkgreen;
  border-width: 2px; 
  border-style: solid;
  padding: 6px; 
  width: 100%;  
}
.img2 {
  float: left;
}