Are ads based on content of page only?

Or also on theme of website? How is 'theme' determined?

[ari11210]

Are the adsense ads displayed by google based only on the content of the page? For example, if my website is about green widgets, but I have one page about blue widgets, will that page's ads be influenced at all by green widgets?
On my site I am seeing that the ads are more or less targeted to the content of the page itself, but sometimes I see general ads that are more appropriate to the general theme of the site, not the page. How does google determine what the 'theme' of the site is to display these ads? Is it looking at meta tags? DMOZ categories? Any other ideas?
Thanks
Aaron

[ken_b]

It does seem like Google assigns a "site theme" that they occasionally use to choose which ads are displayed.

I tend to think this comes into play when available ad inventory is low for the page topic.

[europeforvisitors]

How does google determine what the 'theme' of the site is to display these ads? Is it looking at meta tags? DMOZ categories? Any other ideas?

Google isn't saying, but I'd guess that it's looking at keywords and keyphrases that it finds repeated on many different pages.

[hunderdown]

Another factor may simply be what the keywords are for which there are ads. If you have a page about "blue widgets" and there are no ads for them, then you'll get "widget" ads. Or even "purple widget" ads.

[europeforvisitors]

"Theme" is most apparent on diverse sites that have a lot of subtopics under an "umbrella topic." My site, for example, is about travel on a continent, and the subtopics encompass everything from hotels to different types of cruising to individual destinations. On pages that don't have targeted ads, I'll often see ads for a certain transportation vendor. Why? It could be because I've got an affiliate link for that transportation topic on every page, or maybe the vendor has bid on general travel-related keyphrases for the continent.

[ari11210]

To better explain my questions, I have a site that deals with PalmPilots, so most of the pages have ads that are Palm related. But, I have one page that doesnt mention Palm anywhere on the page, yet it is still getting Palm ads. So how is adsense determining the 'palm' theme?
thanks again

[arrowman]

I have a site that deals with PalmPilots, so most of the pages have ads that are Palm related. But, I have one page that doesnt mention Palm anywhere on the page, yet it is still getting Palm ads. So how is adsense determining the 'palm' theme?

Links to / links from may be a factor.

And the domain.

And the Adsense account id.

[howiejs]

I see theme ads based on the site when launching new pages - then they seem specific

for "smaller" pages (niches) they go back to the theme of the site