function makeItBig() 
{

var winx = document.viewport.getWidth();
var winy = document.viewport.getHeight();

var oW = 1024, oH = 768;

	if (winx/winy > oW/oH)
	{
		winy = winx * oH / oW;
		winx = winx; 
	} 
	else 
	{
		winx = winy * oW / oH;
		winy = winy; 
	}

	$('fullbg').setStyle({
	  'height': winy+"px",
	  'width': winx+"px",
		'visibility': 'visible',
		'marginTop': '-'+winy/2+'px',
		'marginLeft': '-'+winx/2+'px',
		'top':'50%',
		'left':'50%'
	});

}

Event.observe(window, 'load', function() {
 	makeItBig();
});

Event.observe(window, 'resize', function() {
 	makeItBig();
});