Just asking myself does google have any "banned words"?! I bet it will mark your website if it's finding adult words on it, like porn,etc... but how it's acting if he found words like 'access denied'... also how google known if a website have adult materials or it's just a site or a magazine for teenagers? does the google bot read the image and try to find skin color?
Like read an image, detect how much of it it's skin color, yellow the color of the skin , so the crawl can detect if there are dressed or undressed chicks on a site?!
I think it uses some sort of filter for PageRank. For example, many pages on http://xkcd.com/ have a PR of 5 or higher, except this page (Caution: Contains coarse language. Viewer discretion is advised). I doubt Google is advanced enough to look at the individual pixels of pictures to determine if they are pornographic, especially since skin color varies widely from person to person and is dependent upon the quality of the picture. Any site that has adult content is likely to be easily identified as an adult site by text-based content since they would probably try to rank for keywords such as ***, ****, ***, ****, ****, *** and **** (and possibly even *****, ***** and ******).
AKA poison words. Having these words on a page that has adsense can also cause google ads to stop showing as well. google will look at the context of how the phrases on a site are used, they will apply a filter to the page/site if it triggers a condition. e.g. if you have the keyphrase h**d j*b as a phrase multiple times on a site it can trigger a filter even tho the 2 words are legitimate words to be used on any site.
I assume that Google would find it easier to list an adult site by the text on the page. I think most adult sites tag their pictures with adult oriented words anyway, that way their audience finds exactly what they are looking for. I know if I ran an adult site, I wouldn't be fishing for non adult traffic, but maybe that's because I have kids. Now that I think about it, the adult filters do a much better job these days then they did five years ago. That probably is a combination of the search engines becoming smarter about detecting adult material, and the adult site owners becoming smarter about attracting their key audience. Anyway I don't believe they scan pictures for adult material, just the text.
No they don't scan images, but you should read the full TOS for Adsense if you want to make sure that you are within the rules as far as language and content.