Use CSS to set the background-color of the document to yellow.
<html>
<body style="@(16):yellow;">
<h1>This is a heading</h1>
<p>This is a paragraph.</p>
</body>
</html>
<html>
<body style="background-color:yellow;">
<h1>This is a heading</h1>
<p>This is a paragraph.</p>
</body>
</html>