It was officially announced on April 9, 2010: Google would use site speed as a factor in determining search rank. Although Google said that this would affect "fewer than 1% of search queries," it was interesting to note that several comments posted in reaction to this announcement expressed concern about the impact of third-party code snippets and content (including Google's own Analytics and AdWords code).
Of course, search rank is a second-order concern for most performance analysts. The direct impact of response time on such metrics as user engagement, customer satisfaction and revenue is much more top-of-mind. (Although, in an interesting sort of feedback loop, this impact is one of the reasons Google cited for taking site speed into account for search rank!) Keynote offers a number of features to help triage and diagnose performance issues caused by third-party content, including Object Trending and Virtual Pages.
An Object Trending graph breaks down a web page's performance data based on each domain from which the content on the page originates. As a simple (but timely) example, a quick look at an Object Trending graph in the MyKeynote portal confirms that Facebook's outage on September 23 was not caused by a third-party domain:
The purpose of this post is not to pile on Facebook, but it's interesting to observe the cascading effect their outage had on the performance of other sites at the time. People Magazine experienced a spike in response time and a drop in availability:
Now let's take another look at the performance of this page, this time viewing an Object Trending graph. Sure enough, it's easy to see the effect of the facebook.com domain on People Magazine's performance.
Certainly gives one a graphic(al) appreciation of how social networking is increasing the interconnectedness of online technology as well as online people!