Google released a new tool “Gadget Checker” to help developers catch many common errors in iGoogle gadgets, before submitting their gadget to the Directory, such as missing ModulePrefs attributes and missing images, scripts or stylesheets. It also makes suggestions for avoiding common latency traps, like unused API libraries, and for internationalizing your gadget. Simply load a gadget and run the tests, and you may find that you've fallen into one of the common problems. If so, there's advice in the gadget on how to address the issue.

More info: Gadget Checker | iGoogle Developer Blog