var rollClass= "roll";
var overSrcAddOn= "_over";
var preLoads = [];

function preload(){	
	var oversrc;
	var imgs = [];
	var inputImages = [];
	var allImages = [];
	imgs = document.images;
	var inputImages = document.getElementsByTagName('input');
	for(var i=0; i < imgs.length; i++){
		allImages.push(imgs[i]);
	}
	for(var i=0; i < inputImages.length; i++){
		if(inputImages[i].type=="image"){
			allImages.push(inputImages[i]);
		}
	}
	
	for(var i=0; i < allImages.length; i++){
		if(!DOMhelp.cssjs('check', allImages[i], rollClass)){
			continue;
		}
		oversrc = allImages[i].src.toString().replace('.', overSrcAddOn + '.');
		preLoads[i] = new Image();
		preLoads[i].src = oversrc;
		DOMhelp.addEvent(allImages[i], 'mouseover', roll, false);
		DOMhelp.addEvent(allImages[i], 'mouseout', roll, false);		
	}
}

function roll(e){
	var t = DOMhelp.getTarget(e);
	var s= t.src;
	var lastStop = s.lastIndexOf('/');
	var path = s.slice(0,lastStop+1);
	var fileName = s.slice(lastStop+1);
	if(e.type=='mouseover'){
		fileName = fileName.replace('.', overSrcAddOn + '.');
	}
	if(e.type=='mouseout'){
		fileName = fileName.replace(overSrcAddOn + '.', '.');
	}
	t.src = path.concat(fileName);
}

DOMhelp.addEvent(window, 'load', preload, false);