Modal forms are very popular nowadays. While they can be confusing at times they aren't difficult to set up if you have the right tools.
There are several modules available for Drupal 7 that would serve our purpose. I've found Simple Dialog to be the easiest to use and will demonstrate that here.
Want to have a "block" element move up and down the page when the page scrolls? Easy. I'll show you how to get this up and running with jQuery Scroll Follow and Drupal 7.
Javascript is a programming language used to dynamically modify HTML. It is "client side" meaning it is run in the web browser. Javascript is sent to the browser along with the HTML.