I am not a 100% sure if this is new, I know Google has been testing many variations of @SEMantiks tweeted that Sitelinks now have their own Instant Previews.
Yes, when you go to a sitelink, and hover over it, a preview may show up.
Here is a screen shot, click on it to enlarge:
Is this new?
There is some new discussion around preview tests by Google at UK Business Forums.
Forum discussion at UK Business Forums.


Comments:
Thomas Langel
09/22/2011 02:15 pm
Few more screenshots: http://sem-blog.com/neues-google-serp-layout-215/ (german)
Jaan Kanellis
09/22/2011 02:34 pm
So does Google Analytics count that as a page view then?
Jaan Kanellis
09/22/2011 02:34 pm
So does Google Analytics count that as a page view then?
WebOfficer
09/22/2011 02:54 pm
Good time to take your internal category pages and make them interesting if this persists.
Zaitbahajji
09/22/2011 02:55 pm
That's totally new for me! Thank you
BrianChappell
09/22/2011 05:29 pm
Not just on sitelinks. Example here: http://www.flickr.com/photos/brian-chappell/6171111340/in/photostream
Moses
09/23/2011 11:40 am
This feature is useless, how to permanently disable it?
Phoenix_the_II
09/23/2011 05:27 pm
There is an google chrome extension that disables the google preview entirely!https://chrome.google.com/webstore/detail/bfnjgldhekfocbckppcoahkkdhmfmacp?hl=en
Skraggy
09/27/2011 11:05 am
nope, the javascript would not execute since google is just showing it's cached preview of the page