Hi Valdo909, and welcome to WebmasterWorld. Yes, if you're trying to learn HTML and CSS you should obviously learn the latest version which is HTML 5 and CSS 3 otherwise you'll be learning old technology.
HTML 5 is what all the new browsers and cell phones run, you can make responsive websites that resize and change based on the scale of the device.
To speed you along, you may want to start with an HTML 5 framework, there are many. I personally like Twitter Bootstrap as it has EVERYTHING you need to do just about anything. I was impressed.
I'd go for polyglot HTML5 instead of plain HTML5 as it gives structure and well formed-ness over "tag soup". CSS3 is a no brainer of course.
Next I'd use a platform as firefox to learn it on the client side and apache on the server side. By all means stay away from IE - it's outright evil while learning as it does not behave properly. In the end you will have to deal with IE, but it's best done after you "get" how the standards work so you can work around the bugs and missing features of IE instead of being limited by them in your thinking.
>>By all means stay away from IE - it's outright evil while learning as it does not behave properly. In the end you will have to deal with IE,
i try to write code that is utterly standards compliant, i don't use workarounds, if something isn't supported by a browser, i try to make it so those users don't realise there would have been extra functionality if they'd been usign something different. i develop with opera primarily.
I just joined myself, didn't know where to start posting, but I also suggest Less Framework. Google(Yahoo/Bing) it and you will find it on the first link or two. I love Less Framework but I will check out Twitter Bootstrap too.