var ref = document.getElementById("blende");
var speed = 15;
var heightStep = 10;
var height = 0;

function startBlende() {
  setTimeout("step()", speed);
}

function step() {
  ref.style.height = height + heightStep + "px";
  height += heightStep

  if(height <= 402)
    setTimeout("step()", speed);
}

window.onload = startBlende;