^^CSS normalize, reset; valori di CSS del browser.

Valori di CSS del browser. Default CSS styles

If you open a plain HTML file, the browser will have some default styling, like a bit of margin around stuff to make plain pages still be visually acceptable and readable. This can slightly vary between browsers as well.
The stylesheet Normalize.css and others are overwriting the default styles to make it all the browers look the same and to build your styling on top of it without interference.

prompt: quali sono i valori degli attributi html e css di default di firefox browser?

you can find the full list of all styles in each User Agent Stylesheet in the following locations:

• Mozilla Firefox: https://dxr.mozilla.org/mozilla-central/source/layout/style/res/html.css
  https://searchfox.org/firefox-main/source/layout/style/res/html.css
• Google Chrome: https://chromium.googlesource.com/chromium/blink/+/master/Source/core/css/html.css
• Safari (WebKit): https://trac.webkit.org/browser/trunk/Source/WebCore/css/html.css
• Internet Explorer: You can't view Internet Explorer's UA Stylesheet because it's not open source.

reset, normalize  css

1. https://code4life.it/guide/resettare-il-css-predefinito-dei-browser  fornisce 3 esempi, che danno idea, e esploro qui sotto
   1. normalize.css  https://csstools.github.io/normalize.css/  questa e' l'ultima versione, fatta da altri poiche' l'autore originario ha lasciato.
2. reddit  danno l'idea, e ulteriori esempi
   1. https://piccalil.li/blog/a-more-modern-css-reset/
   2. https://tailwindcss.com/docs/preflight
3. https://www.webfx.com/blog/web-design/css-tip-1-resetting-your-styles-with-css-reset