<div id="flux">flux html  flux html flux html flux html flux html flux html flux html flux html flux html flux html flux html flux html flux html flux html flux html flux html flux html flux html flux html flux html flux html flux html flux html flux html flux html flux html flux html flux html flux html flux html flux html flux html flux html flux html .</div>
<div id="gaucheA">Lorem ipsum dolor sit amet, consectetur adipisicing elit.</div></section>
<div id="gaucheB">Lorem ipsum dolor sit amet, consectetur adipisicing elit.</div>
<div id="droite">Lorem ipsum dolor sit amet, consectetur adipisicing elit. Repudiandae</div>

#flux{
  width: 300px;
  background-color: rgb(220,220,220);
}
#gaucheA{
  background-color: silver;
  width: 200px;
  height: 100px;
  left: 15px;
  top: 60px;
  position: absolute;
  border: thin blue solid;
  z-index: 2;
}
#gaucheB{
  background-color: orange;
  width: 200px;
  height: 100px;
  left: 45px;
  top: 80px;
  position: absolute;
  border: thin blue solid;
  z-index: 2;
}
#droite{
  background-color: pink;
  width: 270px;
  height: 100px;
  position: absolute;
  left: 130px;
  top: 30px;
  border: thin red solid;
  z-index: 1;
}