Those are the new flex 4 components called Spark, they all start whit <s:...
its the namespace identifier, so s for spark mx for halo, you could if you want declare xmlns:spark in your application header
xmlns:spark="library://ns.adobe.com/flex/spark" instead of
then mxml spark component definitions would look like this
I could have started Learning FLex with 4 version itself
So i think all my efforts are wasted .
But I like FLEX 3 itself and continue to stick with it , hope Adobe keep up the Suppourt for FLEX 3 version for ever .
With flashbuilder you can use both so there is no reason to use flex 4 but use what you have already learnt as you gradually become more familiar with Flex 4 features, Flex 3 will be with us for a while but more as alegacy sdk flex 3 make grow marginally but Flex 4 is where all the development tools for new technology is going to be enhanced. Better to start learning now rather than procrastinate with Flex 3, Remember that a new flashplayer is about to be released and it is much more powerful than the existing release of flashplayer, to get the full benefit of flashplayer 10.1 you need Flex 4
Thanks David for the valuable suggestions .