CSS3 flat responsive tabs
Simple, flat, responsive, css3 only tabs. Note that you can definitely use ul>li approach instead of divs for tabs. I just wanted to do it this way. Also there are tons of possibilities for "switch tab" animations/transitions. Just play around with it.
Update I've added some simple animations for the content. Uncomment and choose one. Also if you don't like the rounded borders, just remove them :). I will play around with label:hover transforms a bit next.
Feel free to comment !