I recommend using <meta name="viewport" content="width=device-width, initial-scale=1" />. I also find that once that is, it will have a major increase of font size and some image sizes for some browsers including on phones. Also, there is such a thing as an Apple Touch icon and a Windows tablet/phone icon for what displays upon desktop or main page icons being created for a website. I at least know Apple icons are normally PNG and like <link rel="apple-touch-icon" href="https://gugquettex.com/favicon.png">. Windows things require more. Also, external CSS files may be cached for your website on client side. What that may mean is even though you update say in my case gugquettex.com/master.css it will look like it went unchanged until you visit that file and reload it. I have done CSS fixes today so if this is recent to you then you may want to reload that.
I say always provide a fallback for incompatibility if you can and should. Like for font, px, then rem. For icon, GIF then if not that PNG or maybe ICO works well for me. word-wrap: break-word and overflow-wrap: break-word for older things break word only when it would be a longer thing than your width and keep words and things like one in tact otherwise. Meta description of pages comes highly recommended. If you can correctly, try for <meta charset="UTF-8">. These are just good practices I know of, there may be more. Like my recommended font size is in rem but with px as fallback. You can set font size twice and it won't error out, later is like one shown.