I have made a website in simple HTML and CSS (no JS).

I hope it would be compatible with as many browsers as possible.

Is there a free and open source solution that can test and reveal the oldest version of each browser compatible with my site? I want to be able to say something like: This site is compatible with FF v60, Chromium v50, Safari vxx, etc.

Or make a compatibility table so users can know that this was tested.