I've written a small addon to remove the Google Chrome advert on the google.com page when using the Firefox rendering engine.
I use Adblock, but without some effort, you cannot remove divs like this.
This code simply calls the existing function on the google page that closes the div and keeps that info in a cookie for google to remember.
You shouldn't have to deal with this annoying advert again.
Please note: If you use any other variation of google.com, such as google.co.uk or google.jp, you need to ensure that it is added in the plugin. It's easy, just open it up and replace ".com".