I'm interested in finding out how Google reacts to a request for an ad for a page it knows to be a 404

It's against Google TOS, if I remember correctly. A potential reaction may be a ban if they find out. And your reaction to this may be a "I've been banned thread".

Ya, no error pages, I remember ASA saying it is ok to place ads on "thank you" contact us or similar service pages if they have enough content on them..

Thanks for the quick replies. That's made my mind up and saved a bit of messing around.

I did read the T&Cs but could not see a specific reference to this, I suppose it's impractical for G to list all scenarios.

From the Adsense TOS

Section 5 - "Prohibited Uses"

"You shall not, and shall not authorize or encourage any third party to: [...] (v) display any Ad(s), Link(s), or Referral Button(s) on any error page, on any registration or "thank you" page (e.g., a page that thanks a user after he/she has registered with the applicable Web site) [...]"

Aaaaargh!

I hate it when people do what I've just done.

As mzanzig points out, it's there (I missed it - I'll blame the very late night and lack of caffeine).

Maybe we should think up a suitable self-administered punishment for posting something stupid.

I hate it when people do what I've just done

Err, you have NOT done what I have done. You read the document and did NOT find the section. I read the document and DID find it.

<g,d+rvvf>

Concerning the "thank you" pages:
See AdSense Advisor's post here:
[webmasterworld.com...]

However, if your sales confirmation pages also contain other text about your business or product, AdSense can provide a relevant 'next step'

Err, you have NOT done what I have done. You read the document and did NOT find the section. I read the document and DID find it

You may have misunderstood.

I read it as the OP saying that he hates it when people post a question in the forums without thoroughly reading the TOS first. 'As he has just done...'

I used to do a workaround: 404 redirect to home page! :-P

p/g

I used to do a workaround: 404 redirect to home page!

The way I understand it, that could possibly have repercussions for you in the organic SERPs.

I don't think there's any TOS issues with putting a search box on a 404 page.

Your host may already be placing adsense on 404 pages. mine was til I added a custom 404.

Barry pointed out [seroundtable.com] that we have been here before [webmasterworld.com] in an older discussion.

...our policies were designed to prohibited the placement of ads on non-content pages, so you'll need to use your discretion to determine on which types of exit pages it would be appropriate to display Google ads. -ASA

My content management tool creates a 404 page using my standard navigation area where Adsense is included, I can NOT change that. Does that mean I do violate the TOS?

Any idea what to do?

adfree - You need to create a custom 404 page and redirect to that custom page. I use Joomla and that's exactly what I do.

Any idea what to do?

if($_SERVER[PHP_SELF])!= '404.shtml'){
show ads;
}

My content management tool creates a 404 page using my standard navigation area where Adsense is included

Yikes. My programmer is fixing this now. These are errors that are more likely to occur innocently on large sites.

What about 404's that redirect the user back to the home page? Plenty of content there.

Now you guys tell me :)

I've had Adsense on my custom 404 page for about 1 1/2 years. Just removed it!