function topNavRollover(obj) {
 var VarTestSelectedState = new RegExp('-selected');
 var VarTestRolloverState = new RegExp('-rollover');
 var VarTestDefaultState = new RegExp('-default');
 var VarAddRolloverString = obj.src.replace(/-default/, '-rollover');
 var VarAddDefaultString = obj.src.replace(/-rollover/, '-default');
 
 if (VarTestRolloverState.test(obj.src)) {
  obj.src = VarAddDefaultString;
 } else if (VarTestDefaultState.test(obj.src)) {
  obj.src = VarAddRolloverString;
 } 
 
}