Ask HN: How do Software Engineers/Developers deisgn for the web?

I am an Android software engineer starting to work on a side project that requires a web app.

On android, I used to use the gui editor to get the rough GUI (layout, size, proportions) I wanted and then finalized it in xml/java.

I was wondering how I could go about doing so on the web?

I started using React + BlueprintJS to get all the components I needed, but everything looks very ugly without having CSS hacks (or custom styles) all over the place.