I must have gone through 100+ posts on Stackoverflow but without a solution!

I’m creating a document for print using HTML and CSS, and I’m going to export it to PDF. It’s a two-column layout, and I want to add a sidebar that’s aligned to the top right. The document is several pages long, and there could be other sidebars as well on later pages. There’s a simplified version of the markup below. It’s not working – is it possible?

I currently did not understand what happened, because it worked before