Minimalist Iframe Page with Banner

I have a single link that needs to load inside an iframe as the main focus of a clean, modern page. To its right I want a static banner area (300 px wide is fine, but feel free to suggest best-practice dimensions). The overall look should stay minimalist—ample white space, subtle typography, no visual clutter—so that the content inside the iframe remains the hero.

What I will hand over:
• the URL to embed in the iframe
• the banner image or code snippet when you’re ready to drop it in

What I expect back:
• one self-contained HTML/CSS file (a little vanilla JavaScript is okay if you need it)
• a working, publicly accessible URL I can share immediately with clients—GitHub Pages, Netlify, Vercel or any similar free host is acceptable as long as no login is required to view it

The banner must stay visible while users scroll the iframe content; everything else can scroll normally. Please keep the code neat, commented where it matters, and mobile-friendly (simple responsive tweaks will do).

Let me know your estimated turnaround and if you need any other assets to get started.