anchor.diff:  			CheckboxInputElement checkbox = event.target as CheckboxInputElement;
   			if(checkbox.id == "ShowJoinMessages")
   				setJoinMessagesVisibility(checkbox.checked);
  +			if(checkbox.id == "PlayMentionSound")
  +				setPlayMentionSound(checkbox.checked);
   		});
   	
   		//setup saved variables
  
positive.code: 				setJoinMessagesVisibility(false);
  			
  			(querySelector("#ShowJoinMessages") as CheckboxInputElement).checked = getJoinMessagesVisibility();
  		}
  		
  		addChatTab("Global Chat", true);
  
negative.code: part of coUclient;
  //TODO: should we limit chat history so that it doesn't go on forever?
  
  //TODO: change error message to be an overlay over the chat pane
  
  class Chat
  {
  