Where i am using HTML and CSS in notepad.

Answer 1

Save the arquive with the extension .css and .html. And open in browser.

Answer 2

save as fiie with required extention html or css
I think dreamweaver is much handy to use for coding

Answer 3

just one note : you can keep both files in the same folder, or in separate but you have to mention the full path in declaration @ html file