Popup the error message with previous value and new value with difference 

currently user need to identify, which particular error is increased and by how much  percentage e..g 404 increased from 1% to 1.3%, there was an increase of 0.3% in last 15 minutes!!

A message like above will help.

Configuration:  
Message should fade away after 10 secs, opacity of 0.7 or 0.8 and a Growl notification.