function rolloverFunction(){
	var upImages = document.getElementsByTagName("img");
	var overImages = new Array();
	// loads rollover images and sets up event listeners
	for (var i = 0; i < upImages.length; i++){
		if ($(upImages[i]).className == "rollovers"){
			
			var upImage = $(upImages[i]);
			var upImageSrc = upImage.getAttribute('src');
			// grab the up image src
	    var imageType = upImageSrc.substring(upImageSrc.lastIndexOf('.'), upImageSrc.length);
	    // compute the over image src
	    var overImageSrc = upImageSrc.replace(imageType, '_o'+imageType);
	    
	    // assign new image object to that src
			overImages[i] = new Image();
			overImages[i].src = overImageSrc;
			attachEventListener(upImage,"mouseover",rolloverImageChange,false);
			attachEventListener(upImage,"mouseout",rolloffImageChange,false);
		}
	}
	
	function rolloverImageChange(){
		var curImage = $(this.id);
		var curImageSrc = curImage.getAttribute('src');
    var imageType = curImageSrc.substring(curImageSrc.lastIndexOf('.'), curImageSrc.length);
    var newImageSrc = curImageSrc.replace(imageType, '_o'+imageType);
    curImage.src = newImageSrc;
	}
	
	function rolloffImageChange(){
		var curImage = $(this.id);
		var curImageSrc = curImage.getAttribute('src');
		var newImageSrc = curImageSrc.replace("_o.",".");
		curImage.src = newImageSrc;
	}
	
}

attachEventListener(window,"load",rolloverFunction,false);