var n = 0;
var increment = 5;	//opacity increment - must be a factor of 100
var timeToFade = 100;	//time image takes to appear in milli seconds
var faderTimer = null;

function fadeBg(){
	bgObj = document.getElementById('thumbnails');
	faderTimer = setInterval('changeOpacity(bgObj)',timeToFade/(100/increment));
}

function changeOpacity(bgObj){
	n += increment;
	bgObj.style.MozOpacity = n/100;
	bgObj.style.opacity = n/100;
	bgObj.style.filter = 'alpha(opacity=' + n + ')';
	if(n >= 100) clearInterval(timer);
}