.introduction
{
  color: brown;
}

#introduction
{
  color: green;
}
.introduction_1
{
  color: yellow;
}

h1 + p
{
  color: pink;
}

p em
{
  color: gold;
}

h1
{
  text-align: center;
}

body
{
  background-color: grey;
}

.flottant
{
  float: left;
}