To build and test the site locally, open the root directory in a terminal and run python3 build.py, then open http://127.0.0.1:8080 in a browser. Hit Ctrl+C in the terminal to stop testing. Requires Python 3+ and .NET SDK 9+.
To test just the raw HTML/CSS/JS pages locally (no Blazor), open the root directory in a terminal and run python3 -m http.server, then open http://127.0.0.1:8000 in a browser. Hit Ctrl+C in the terminal to stop testing. Requires Python 3+.
Before testing the site locally, first you need to clone/download the repository, and then open the repository's root directory in a terminal. E.g. in Windows you can do this by navigating to the root directory in file explorer, then right-clicking on any empty space, and pressing "Open in Terminal". Alternatively (in any operating system), open the "Terminal" app, then type cd path/to/repository and replace path/to/repository with the path for where you cloned/downloaded the repository, e.g. cd C:\Users\JohnSmith\Documents\github\popruns.github.io.