Back in 2007, I wrote about a Yahoo patent describing how Yahoo! might crawl a webpage, and then recrawl the same page around a minute later to see if any of the links on the page had changed. It might do that to try to identify what it called “Transient Links,” or links that pointing to things like advertisements that might change on every visit to a page, which aren’t links that the search engine would want to crawl and index. The post is A Yahoo Approach to Avoid Crawling Advertisement and Session Tracking Links.
Google was granted a patent this week on a similar topic that looks at “transient” content on web pages. While this kind of content might include advertisements as well, that change regularly on return visits to page, it could also include things like current weather forecasts (Warrenton, Virginia, 40 degrees and cloudy) for example. That kind of content changes on a regular basis, but often has little to actually do with content found elsewhere on a page.
Google would want to be able to identify transient content so that it wouldn’t index pages based upon it, and it wouldn’t show advertisements that focus upon it either.