XML/SVG/viewBox

Set viewBox for SVG

<?xml version="1.0" encoding="iso-8859-1"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 20001102//EN" 
 "http://www.w3.org/TR/2000/CR-SVG-20001102/DTD/svg-20001102.dtd"> 
<svg width="800" height="400" viewBox="0 0 800 400">
    <g> 
      <rect style="fill:red;"
        x="0" y="0" width="100" height="50"/>
    
      <line x1="0" y1="24" x2="100" y2="24"
            style="stroke:white;stroke-width:2"/>
    
      <line x1="49" y1="0" x2="49" y2="50"
            style="stroke:white;stroke-width:2"/>
    </g>
</svg>