jquery validator show message based on validator outcome

jquery validator show message based on validator outcome

I want to show error message based on outcome of validate. Like in my case, I am validating feed url. There couls be case where url is not reachable, or feed is valid. I want to show message accordingly.  

jQuery.validator.addMethod("feed", function(value, element) { var retVal = true; //Ajax call here which returns  var retMsg = ajax() if(retMsg == "one") { //Show error as "not valid url" } else if(retMsg == "2") { //Show error as "not reachable url" } return retVal; }, << CUSTOMIZE MESSAGE HERE BASED ON Validation OUTCOME >>);