How to insert SVG into HTML

Simplest example drawing an ellipse

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" 
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title> XHTML document </title>
</head>
<body>
     <svg xmlns="http://www.w3.org/2000/svg" width="300" height="200">
          <g>
               <ellipse cy="20" rx="45" ry="50" 
                        transform="translate(45,30)" />
          </g>   
     </svg>
</body>
</html>