Yes, it's supported in all browsers in that it reads out text to someone who can't see the image; but the alt text doesn't necessarily display on screen (which I guess is not the primary intention of alt text. I'm not sure what the specs say.)
Originally Posted by John_C
Ah, I thought you just meant style sheets targeted to mobiles via @media queries. E.g.
Regarding the handheld stylesheets: I haven't used them but I intend to.
Many mobile devices take no notice of media="handheld", so it's kind of a dud technology. For example, iPhones ignore it, and most other smartphones, I believe.
<link type="text/css" href="screen.css" media="screen,projection,tv" >
<link type="text/css" href="smallScreen.css" media="screen and (max-width:751px)" >