Problem
I need to open a new window without any scrollbars, toolbars and other same things
The new window should have only white background and some info inside
Here is the screenshot how it should be:

What I've tried: I've already read some articles: https://www.w3schools.com/jsref/met_win_open.asp Open new popup window without address bars in firefox & IE
and they say that this should be done the following way:
window.open("https://www.w3schools.com", "_blank", toolbar=no,scrollbars=no,resizable=yes,top=500,left=500,width=400,height=400");
But this doesn't work.
My Code
<head>
<title>JS unload Event Demo</title>
<script>
function myFunction() {
window.open('https://www.w3schools.com/', 'Hello', "toolbar=no,scrollbars=no,width=400,height=400");
}
</script>
</head>
<body onload="myFunction()">
</body>
</html>
It gives a new window with all these things, that I don't need. How can I solve it?