Need help with div, layers & containers

Hey,
I’ve been working for a web company for the last 3 years and we have been using tables and css for fonts, backgrounds, et cetera but I keep seeing sites with DIV and Layer. I keep hearing about containers. I want to learn how to make a site with DIVs & CSS. Anybody know a good place to start? Like I look at a site but I can’t figure out how they set the location of the layers and how do they make it look good in all of the screen resolutions? Please help it would be greatly appreciated.
GQ1000!!!