This site's is made with the default appearance your web browser provides in mind. This offers you a (typically) easy way to customize the appearance of documents on the web. This approach should consistently apply your changes to all pages here, and most other websites as well. The exceptions to this would be sterilized sites such as Google, and more artistic sites such as this one here. If you find your own website doesn't fall under those categories, consider swapping things to use suitable generic font families. If you've got something decorative where color doesn't matter (like the gradient on the sides of this document), I recommend using "currentColor" if appropriate.
If you don't know how to modify yours, pick something here you find fits your situation best: