When trying make Google Site appear at your own custom web address (e.g. how to make your Google Site appear at www.example.com) one step that seems to confuse many users is when they try to verify ownership of a custom domain URL as described here. At the time of writing, the terminology used in the Google support article is misleading. It states:
Make sure you've added your site to your Google Webmaster Tools account.
In the above sentence, by 'site' they are referring to the custom domain URL, NOT the google Sites URL. So what it really should say is:
Use the red Add a site button and enter the domain (not your sites.google.com URL) that you want to map to your site. So if you want to map www.example.com to your site add example.com and use the blue Continue button.
The full instructions for mapping a custom domain (including the above) can be found here:
A help forum thread discussing this with user experiences can be found here: