[thelist] Learning CSS - what's the # for + any good tutorials?

[Simon Willison]

I'm currently refreshing my knowledge of CSS - I haven't looked at it in ages and things seem to have changed since my last forays... I keep seeing style sheeets with this kind of thing in them:

#title { position:absolute; top:200px; left:300px; width:1400px; padding:0; margin:0; z-index:2; }

First of all, what does the # do ? Secondly (and more importantly) does anyone know of any good CSS tutorials which cover the more recent advances in CSS (selectors and such like) while maintaining a healthy emphasis on what works in what browsers?

Cheers,

Simon