var offIndicator="_off";
var overIndicator="_over";
var preloadIndex=0;
var imgNames=new Array();
var loadImgs=new Array();
var offExpression = "/"+offIndicator+"/gi";
var overExpression = "/"+overIndicator+"/gi";
function swapOver(imageName){
	var imageSource = eval("document.images['"+imageName+"'].src");
	var newImageSource = imageSource.replace(eval(offExpression), overIndicator);
	document.images[imageName].src = newImageSource;
}
function swapOut(imageName){
	var imageSource = eval("document.images['"+imageName+"'].src");
	var newImageSource = imageSource.replace(eval(overExpression), offIndicator);
	document.images[imageName].src = newImageSource;
}
function preloadImgs(){
	for( i = 0; i < document.images.length; i++ ){
			if ( document.images[i].src.search(eval(offExpression)) > -1 ){
				imgNames[preloadIndex] = document.images[i].src.replace(eval(offExpression), overIndicator);
				preloadIndex++;
			}
	}
	for( i = 0; i < imgNames.length; i++ ) {
	  	loadImgs[i] = new Image;
	  	loadImgs[i].src = imgNames[i];
	}
}