Yes, this would be the best. Web site provides the content and the browser (user agent) decides how best to render it, potentially different than how the web developer would want it.
I remember users setting their default font sizes to 30px, then complaining when they hit the one piece of text on a website with an undefined text size.
User-defined formatting hasn't worked since CSS was introduced.
Remember when browsers supported user styles out of the box and put them in a somewhat discoverable location?