Browser safe fonts, avoided by CSS?

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Well, my basics are not that strong, so I'll assume a browser safe font is one which is easily displayed on all browser and its a safe bet; hence browser-safe.

Well the question is: I want non-standard fonts like Vivaldi for the content, but I was told they won't appear on a browser, so will putting it in a themes's CSS help me get by this? If not how can I use non-standard fonts??