your not gona learn css over night. it will take time and experince to understand what is going on. your best off learning from what other peoples work.
here are some quick links.
http://www.glish.com/css/
http://www.tjkdesign.com/articles/one_html_markup_many_css_layouts.asp
http://www.w3schools.com/css/default.asp
http://www.sitepoint.com/subcat/css
http://www.digital-web.com/articles/fluid_thinking/
everthing is working correctly now right?
good luck.