Well, who is right then

Quite often I read a story and the phrase 'I could care less' crops up.

For example 'I could care less about you.'

As far as I am aware, in the good ol' UK we say 'I couldn't care less about you.'

So which is right or are they both right?

Hugs

Sue

PS, Another good one is the use of 'is all,' rather than 'that's all.'but I'm not sure about the context on that one.