Barra a comparsa

https://www.w3schools.com/howto/tryit.asp?filename=tryhow_js_snackbar

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1">
<style>
#snackbar {
  visibility: hidden;
  min-width: 250px;
  margin-left: -125px;
  background-color: #333;
  color: #fff;
  text-align: center;
  border-radius: 2px;
  padding: 16px;
  position: fixed;
  z-index: 1;
  left: 50%;
  bottom: 30px;
  font-size: 17px;
}

#snackbar.show {
  visibility: visible;
  -webkit-animation: fadein 0.5s, fadeout 0.5s 2.5s;
  animation: fadein 0.5s, fadeout 0.5s 2.5s;
}

@-webkit-keyframes fadein {
  from {bottom: 0; opacity: 0;} 
  to {bottom: 30px; opacity: 1;}
}

@keyframes fadein {
  from {bottom: 0; opacity: 0;}
  to {bottom: 30px; opacity: 1;}
}

@-webkit-keyframes fadeout {
  from {bottom: 30px; opacity: 1;} 
  to {bottom: 0; opacity: 0;}
}

@keyframes fadeout {
  from {bottom: 30px; opacity: 1;}
  to {bottom: 0; opacity: 0;}
}
</style>
</head>
<body>

<h2>Snackbar / Toast</h2>
<p>Snackbars are often used as a tooltips/popups to show a message at the bottom of the screen.</p>
<p>Click on the button to show the snackbar. It will disappear after 3 seconds.</p>

<button onclick="myFunction()">Show Snackbar</button>

<div id="snackbar">Some text some message..</div>

</body>
</html>

https://www.w3schools.com/howto/tryit.asp?filename=tryhow_js_snackbar

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1">
<style>
#snackbar {
visibility: hidden;
min-width: 250px;
margin-left: -125px;
background-color: #333;
color: #fff;
text-align: center;
border-radius: 2px;
padding: 16px;
position: fixed;
z-index: 1;
left: 50%;
bottom: 30px;
font-size: 17px;
}

#snackbar.show {
visibility: visible;
-webkit-animation: fadein 0.5s, fadeout 0.5s 2.5s;
animation: fadein 0.5s, fadeout 0.5s 2.5s;
}

@-webkit-keyframes fadein {
from {bottom: 0; opacity: 0;}
to {bottom: 30px; opacity: 1;}
}

@keyframes fadein {
from {bottom: 0; opacity: 0;}
to {bottom: 30px; opacity: 1;}
}

@-webkit-keyframes fadeout {
from {bottom: 30px; opacity: 1;}
to {bottom: 0; opacity: 0;}
}

@keyframes fadeout {
from {bottom: 30px; opacity: 1;}
to {bottom: 0; opacity: 0;}
}
</style>
</head>
<body>

<h2>Snackbar / Toast</h2>
<p>Snackbars are often used as a tooltips/popups to show a message at the bottom of the screen.</p>
<p>Click on the button to show the snackbar. It will disappear after 3 seconds.</p>

<button onclick="myFunction()">Show Snackbar</button>

<div id="snackbar">Some text some message..</div>

<script>
function myFunction() {
var x = document.getElementById("snackbar");
x.className = "show";
setTimeout(function(){ x.className = x.className.replace("show", ""); }, 3000);
}
</script>

</body>
</html>