function swapNavImg(obj)
{
	filename = obj.src;
	if(filename.indexOf("_ov.") > -1)
	{
		firstpart = filename.substring(0,filename.indexOf("_ov."));
		obj.src = firstpart + ".gif";
	}
	else
	{
		firstpart = filename.substring(0,(filename.length - 4));
		obj.src = firstpart + "_ov.gif";
	}
}