Google Chrome has this user friendly feature that will show the thumbnails of the mostly visited websites by you. It is quite similar to take a print screen. I have noticed that it keep on taking the password protected pages. For example I can see the view of my Gmail, Facebook accounts in the Chrome Thumbnails.
If you working on a shared computer environment this is something you must take into consideration as these thumbnails might gives out any secret information of you out. If it is a regular page that you visit and if it display some of your secrets or secret picture in a password protected page but Google chrome might show it out.
Always use the Remove Thumbnails link below to remove such thumbnails from Google chrome New Tab.