Insert the included header in "index.html." Click inside "index.html" at the location where you want the header inserted, then click "Insert," followed by "Server-Side Include." ...

Create a section for your CSS style sheet in the header of your HTML page. Link to an external CSS style sheet as an alternative for larger stylesheets.

Ryan Boudreaux includes all the code snippets you'll need in this demo of how to create an image hover-preview effect using HTML, CSS, and JavaScript.