DWBI

Stands for "Don't Worry 'Bout It"
Pronunciation: Dew-Bee

Could be used in a rude or friendly manor.
Simply telling someone not to worry about something.

Rude example:

Tom: Hey man what's the answer to number 3
Bill: DWBI
Tom: aw, cmon man!

Friendly example:
Dan: Hey just checking to see if your ankle is ok
Rob: DWBI, it's all healed up I'm ready to go this Sunday