 
     private function loader_ioErrorHandler(event:IOErrorEvent):void
     {
-        trace(event);
+        Alert.show(event.text, "Application IOError");
     }
 
     private function loader_securityErrorHandler(event:SecurityErrorEvent):void
     {
-        trace(event);
+        Alert.show(event.text, "Application Security Error");
+    }
+
+    protected function loader_httpStatusHandler(event:HTTPStatusEvent):void
+    {
+        if (event.status == 404)
+        {
+            Alert.show("Unable to load the following resource \n" + url, "http error");
+        }
     }
 }
 

import com.esri.ags.utils.WebMercatorUtil;

import flash.events.Event;
import flash.events.IOErrorEvent;
import flash.events.SecurityErrorEvent;
import flash.net.URLLoader;
import flash.net.URLRequest;

public class GPXFeed
{

        _loader.addEventListener(Event.COMPLETE, loader_completeHandler);
        _loader.addEventListener(IOErrorEvent.IO_ERROR, loader_ioErrorHandler);
        _loader.addEventListener(SecurityErrorEvent.SECURITY_ERROR, loader_securityErrorHandler);
        _loader.addEventListener(HTTPStatusEvent.HTTP_STATUS, loader_httpStatusHandler);
    }

    // variables
