Sowmya,
Instead of the page backgroud, you can use the CSS styles - position to show the background to strech/fit to screen. Like
<body bottommargin=0 topmargin=0 leftmargin=0 rightmargin=0>
<div style="position:absolute;left:0px;top:1px;width:100%;height:100%">
<img src="background.jpg" style="position:absolute;left:0;top:0;width:100%;height:100%;"/>
</div>
<div style="position:absolute;left:0;top:0;width:100%;height:100%;">
Your page content here. This will be visible on top of the above image.
</div>
</body>