Are you sure the image is in the 'images' folder and named last.png? Are you sure the image is using the right color space RGB and not CMYK.
There's nothing wrong with the code that I can see. What happens if you just try some text:
<!DOCTYPE HTML>
<html>
<head>
<style type="text/css">
body {
width: 100%;
height: 100%;
margin: 0px;
padding: 0px;
}
</style>
</head>
<body>
<h1>Hello</h1>
</body>
</html>