This is an example of a Flex Div with rows inside a column.
The row’s menu is sticky to the header.

The index.php file includes a script, in the link to the style sheet (header), that will make  the browser reload the CSS, just to be sure the users are seeing the website, with the latest CSS updates. This will also work to link files of javascript.

demo

• HTML, CSS, PHP
• Includes: index.html, index.php  and CSS file