I would like to style standard window.confirm without using any additional JavaScript code, only with CSS. Is it even possible? And if it is, how can I do it?
It is not possible. This window is displayed by the browser using the platform's UI kit. It's not in the DOM, not visible from the CSS or Javascript, there's nothing you can do.
However, some very simple jQuery code can do the trick. How about $('a').confirm();
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