Looking for help on Notices

I just recently watched the "Have you seen" on Notices and was very impressed by it's scalability and functionality, especially at the very end of the video where we see images presented with Text box overlays on them. Being completely new to web coding, I am utterly lost when it comes to doing this.

Does anyone have some sample code they could share to insert into the HTML message box that will replicate that? I've googled around a bit trying to find similar but haven't had any luck implementing it.