DennisMatveyev,
<!DOCTYPE HTML>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
body,html{
width: 98%;
height: 90%;
}
html:before {
content: "";
position: absolute;
right: 0;
bottom: 0;
display: block;
width: 0;
height: 0;
border-bottom: 120px solid #006633;
border-left: 120px solid transparent;
}
body:before {
content: "";
position: absolute;
right: 0;
bottom: 0;
display: block;
width: 0;
height: 0;
border-bottom: 100px solid red;
border-left: 100px solid transparent;
}
body:after {
content: "";
position: absolute;
right: 0;
bottom: 0;
display: block;
width: 0;
height: 0;
border-bottom: 80px solid #FFFFFF;
border-left: 80px solid transparent;
}
</style>
</head>
<body>
</body>
</html>