Debugging KML loading problems in Google Maps

I was attempting to load some KML into Google Maps via the KmlLayer class and not having much luck. Nothing was appearing. Unfortunately the KmlLayer class doesn’t provide an event to indicate an error has occurred. So what is available to debug these problems and what are some of the issues that can cause load errors?

• Fiddler may help, although it didn’t give any indication to me about what was going on. But I have seen some HTTP responses with 400 bad request status codes in the past. Unfortunately they didn’t say why the request was bad.
• Check that the KML is valid using Feed Validator. I’ve found this doesn’t work too well with large KML files in IE, so use some other browser instead.
• When Google Maps does server side rendering of KML it appears to do some caching of the data, so if you change your KML, changes may not appear immediately.
• There are limits to the size of KML file supported by Google Maps, have a look at this page to see if this is your problem. I think this is what caused my issues.
• Try loading the KML in Google Earth to see if it’s an issue with the KML or Google Maps’ handling of it.