An example of how to use the CANVAS tag in HTML

canvastest.html

<canvas width="640" height="480" id="testcanvas">
</canvas>
<script>
function clear() {
  var ctx = document.getElementById('testcanvas').getContext('2d');
  ctx.fillStyle = "rgb(0,0,0)"
  ctx.fillRect( 0, 0, 640, 480 );
}
function paint( i ) {
  var ctx = document.getElementById('testcanvas').getContext('2d');
  for( var y = 0; y < 480; y++ ) {
    for( var x = 0; x < 640; x++ ) {
      if( x % 2 == 0 && y % 2 == 0) {
        ctx.fillStyle = "rgb(255,255,255)"
        //if( y > 100 && y < 400 )
        //  if( x > 100 && x < 500 )
        if( ((x * y) & 256) > 100)
          ctx.fillStyle = "rgb(255,128,128)"
        ctx.fillRect( x, y, 1, 1 )
      }
    }
  }
}
function setpixel( x, y, r, g, b ) {
  var ctx = document.getElementById('testcanvas').getContext('2d');
  ctx.fillStyle = "rgb("+r+","+g+","+b+")"
  ctx.fillRect( x, y, 1, 1 )
}

clear()
paint()
for( x = 0; x < 200; x++) {
  setpixel( 100+x, 100+(x/2), 255, 255, 255 );
}
</script>