Soft HTTP Error handling for Twitter API, using jQuery and JSONP. For cross-domain JSONP requests, you cannot handle other HTTP response codes than 200.

JSONPTwitterErrorHandling.js

this.getJSON = function(url, data, callback) {		
		var api = this;		
		$.getJSON(url, Utils.mergeHashes(data, { suppress_response_codes : true }), 
			function(result) {				
				if (result.error === "Could not authenticate you." || 
					result.error === "This method requires authentication.")  
					$.getJSON(url, data, callback);				
				else if (result.error) {
					$.event.trigger( "ajaxStop" );
					api.errorCallback(result.error);
				}
				else 
					callback(result);				
			});
	};