As of right now I believe only Firefox support -moz-border-radius property. I am surprised that twitter uses it.
Are any other browsers planning on supporting this or does CSS3 have something like this in the works?
edit:// also found -webkit-border-top-left-radius and then the CSS3 version
So when is CSS3 coming out?
CSS3 has border-radius. for now, mozilla and webkit based browsers have experimental support, -moz-border-radius and -webkit-border-radius. it's not bad to use them now, as long as you understand they are temporary measures until they are properly implemented. i would expect it's not too long before you see full support for border-radius in mozilla, firefox and IE. (well, hopefully IE)
Because the CSS3 spec hasn't been finalised, Mozilla and Webkit decided to implement their own method of rounded corners, doing it in the correct way, by adding the vendor-specific tag at the front.
This is done so that when the CSS3 is FINALLY released, should they change how border-radius is supposed to work (eg: the order of the parameters), then none of the sites using the vendor-specific methods will be broken. Mozilla and WebKit can just go ahead and implement the W3C style and developers can slowly move over to that.
It's not too surprising that you're seeing some websites using it, especially for something like rounded corners where it's not going to make a massive difference to the user experience. And I mean, it's just IE users who are missing out, and they deserve everything they get.
Any CSS property that starts with a dash (e.g. -moz, -webkit) is a browser-specific property.
This allows browser vendors to experiment with new CSS properties. Doing so is a common part of the process for writing new CSS specs, to allow web developers to see how the properties work and raise issues.
Hence you’ll find a lot of CSS 3 properties, like border-radius currently implemented in some browsers with vendor-specific extensions.
There’s nothing particularly wrong with using these on production sites, as long as you’re aware they’ll only work in the one browser.
CSS 3 should be out any decade now :)
It bugs me when people talk about CSS3 coming out. It's not a complete spec like the previous ones. It has been broken up into separate modules that may increment their versions independently.
So Selectors Level 4 may make Recommendation before CSS Backgrounds and Borders Level 3 does.
So, will CSS3 arrive? Eventually, but not all a once. So don't wait for it, start using it now (where applicable).
Browser-based properties are only meant for interim fixes for that particular browser, and are supposed to be deprecated when either the W3C adopts them into CSS, or not. I wouldn't rely on them to be cross-browser or even be kept for the particular browser.