Webmasters can use the <!– google_ad_section_start–>, <!– google_ad_section_end–> tags to provide Adsense Bots an hint about content that is more relevant for Google Ads.
Do they have similar tags for providing hints to the regular Googlebot ?
Some people think that the googleon and googleoff tags serve a similar purpose and could be used for the purpose of SEO - well that’s correct but they are for the Google Search Appliance and not the public Google web search.
From the GSA Search Crawl Policy:
The Google Search Appliance supports “googleon” and “googleoff” tags, special proprietary HTML tags that can be embedded in the HTML of crawled documents to prevent searching of text between these special tags.
The googleoff/googleon tags disable the indexing of a part of a web page. The result is that those pages do not appear in search results when users search for the tagged word or phrase. For example, some customers use googleoff/googleon tags to comment out a navigation bar in static HTML pages.
You can use googleon/off to tell the Google Search Appliance to ignore portions of a page. Insert <!–googleoff: index–> at the point you want the Google Search Appliance to stop indexing, then insert <!–googleon: index–> where you want it to resume indexing the page.
GoogleOn and GoogleOff tags (which may see live on adobe.com) will be ignored by regular Google spiders or other search engines. They make sense only when used in conjunction with Google Search Appliance or possibly, Google Mini.