I thought I was clear, but . . .
It is my undertanding that you cannot use adsense in error pages.
If that is not true, that opens many possibilities.
"Ad Placement
Up to three ad units may be displayed on each Web site page, but no ad unit shall contain any advertisement in common with any other ad unit. Serving two or more identical ads on a single page constitutes double-serving, which Google does not support.
A maximum of two Google AdSense for search boxes may be placed on a page.
No Google ad may be placed on any non-content-based pages. This includes error, login, registration, "thank you" or welcome pages.
No Google ad or Google search box may be displayed on any domain parking websites, pop-ups, pop-unders, or in any email.
No Google ad may be placed on pages published specifically for the purpose of showing ads, whether or not the page content is relevant.
Elements on a page must not obscure any portion of the ads, and the ad colors must be such that any ad elements, including text and URL, are visible.
Clicks on Google ads must not result in a new browser window being launched."
Ok, here is the Rules straight from G. It specfically says NO error pages.
Was a good idea though.