function resetImages(){
	if (document.images) {
		xob = new Image();
		xob.src = "images/box.gif";
		xob_tick = new Image();
		xob_tick.src = "images/boxtick.gif";
		
		apply_out = new Image();
		apply_out.src = "images/apply_filter.gif";
		apply_over = new Image();
		apply_over.src = "images/apply_filter_over.gif";
	}
}

resetImages();

function rollOver(image,image_src) {
	document[image].src=image_src;
}

function tickBox(what){
	if (document.forms[0]['tb'+what].value == "false"){
		document.forms[0]['tb'+what].value = "true";
		rollOver('box'+what, xob_tick.src);
	} else {
		document.forms[0]['tb'+what].value = "false";
		rollOver('box'+what, xob.src);
	}
}