seleccion = 0;

function pestana() {
l1=document.getElementById("l_1");
l2=document.getElementById("l_2");
l3=document.getElementById("l_3");
l4=document.getElementById("l_4");
l5=document.getElementById("l_5");
p1=document.getElementById("pest1");
p2=document.getElementById("pest2");
p3=document.getElementById("pest3");
p1.style.display="none";
p2.style.display="none";
p3.style.display="none";
}

function pestana1() {
if(seleccion != 1){
  seleccion = 1;
  l1.className = "sel";
  l2.className = "nosel";
  l3.className = "nosel";
  p1.style.display="block";
  p2.style.display="none";
  p3.style.display="none";
}
}

function pestana2() {
if(seleccion != 2){
  seleccion = 2;
  l1.className = "nosel";
  l2.className = "sel";
  l3.className = "nosel";
  p1.style.display="none";
  p2.style.display="block";
  p3.style.display="none";
}
}

function pestana3() {
if(seleccion != 3){
  seleccion = 3;
  l1.className = "nosel";
  l2.className = "nosel";
  l3.className = "sel";
  p1.style.display="none";
  p2.style.display="none";
  p3.style.display="block";
}
}