Between 2008 and 2012 gradients finally appeared in web browsers although as of 2012 they still all required a browser prefix. Opera V12 and greater have them, they've been universal in phones since Opera 12 and by 2016 or so you'd be hard pressed to find ay browser that can't handle them. Old versions of Netscape will have a problem, but in practical terms, they're very well supported across all platforms. Use them without hesitation, sparingly. You're writing a web page not decorating aa Christmas tree.


sizes
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Fig 7.0 Radial gradients work the same way, but they're like, radial.
There's more and better examples at http://dev.opera.com/articles/view/css3-radial-gradients/

radial-gradient(rgb(0, 0, 0), rgb(127, 127, 255));
radial-gradient(rgb(0, 0, 0), rgba(127, 127, 255, 0.5));
radial-gradient(rgba(0, 0, 0, 0.5), rgba(127, 127, 255, 0.5));
radial-gradient(rgb(0,0,0), rgba(0, 0, 0, 0.5) 25%, rgba(127, 127, 255, 0.5) 50%, rgb(127, 127, 255));
radial-gradient(circle at 50% 50%, rgb(75, 75, 200), rgb(0, 0, 75));
radial-gradient(2em 4em ellipse at 70px 80px, rgb(75, 75, 200), rgb(0, 0, 75));
radial-gradient(farthest-side circle at 35% 25%, rgb(75, 75, 200), rgb(0, 0, 75));
radial-gradient(40px circle at 35% 25%, rgb(75, 75, 200), rgb(0, 0, 75));
radial-gradient(rgba(255,255,255,.35), rgba(255,255,255,0) 20%, rgba(255,255,255,0) 21%),
radial-gradient(rgba(0,0,0,.2), rgba(0,0,0,0) 20%, rgba(0,0,0,0) 21%),
radial-gradient(farthest-corner, #f0f0f0, #c0c0c0);