Quote Originally Posted by ekaterinak
Петя: Будешь (хочешь) кофе? / Piter: Do you want some coffee?
Катя: Да нет, наверное. / Kate: Yes, it is not, probably.

What did she mean? Did she say ‘Yes’? Maybe she meant ‘No’ or something else ??????
Actually she meant “No”, but she has been hesitating what she has to say ‘Yes’ or ‘No’.
In this case the word «да» does not mean “yes”. It’s like a parenthesis or even an interjection here. Compare with «Да, ну!», «Да брось», «Да я не знаю» etc. In these sentences «да» has no meaning, it’s “a set of sounds”, the way to delay an answer only, but not “yes”. Do not believe Zadornov.