WordPress.org

Why are there not tooltips for my old posts?

This plugin inserts javascript calls into each post as the post is saved. An option to do this for all existing posts is planned, but not yet added. As a workaround you could update each post once to let the plugin do the work, or wait for a new plugin version.

Where do you get the images from?

Im using a wordpress function I randomly stumbled upon:

Call 'http://s.wordpress.com/mshots/v1/http%3A%2F%2F' with any url (no 'http://') appended, and it will return a screenshot of that page.