DCG: If you check your webserver logs, you'll see visits from Google's AdSense bot, which parses the page's content to figure out what ads to display. Look for a line like:
64.68.87.55 - - [15/Aug/2003:15:41:34 -0400] "GET /index.html HTTP/1.0" 200 1168 "-" "Mediapartners-Google/2.1 (+
http://www.googlebot.com/bot.html)"
in your logs (i.e. the Mediapartners bot is the AdSense one).
Until that hits, it's girl guide cookie ads.
If you start sending huge amounts of traffic, and they review the site, they might manually set it to charity ads if they don't like the content, apparently.