Had better

[meskete]

I think there's just a spelling problem.
The correct structure includes had:
I'd better go now. You'd better hurry.
However, we often don't pronounce the 'd - as we don't pronounce t or d in many other cases:
mustn't, I can't bear/stand/go..., mind the gap, etc.
Sometime you can really hear that slight difference between I'd better and I better but it's such a small thing that it can easily get lost. Still, it shouldn't be left out in writing

[gabber]

"had better" is what [some] grammarians call a modal idiom. It means "should."

[mara_ce]

Does anyone really understand this structure? To be honest, it escapes me.

Had better refers to present or future time, and gives advice about how to stop something going wrong.

I think you'd better leave now. (Before it is too late)
You'd better not drive. (It might be dangerous)

[Huda-M]

'Cause we say - You had better do it, so, i think it will be you had better NOT do it. You had not better do it looks a bit sensless to me................

[xpert]

had better not

[GreyMan]

"had better" is what [some] grammarians call a modal idiom. It means "should."

That's interesting. I though it didn't fit in with any grammatical pattern, even though the meaning is clear.