Freda:

It is a netspeak acronym for "In My Humble Opinion". SOmeitmes IMNSHO (not-so-humble opinion)

Others you may see:
LOL (Laughing out loud)
ROTFLMAO (Rolling on the floor laughi9ng my ass off)
YMMV (your mileage may vary)
IANAL (I am not a lawyer)
BRB (Be right back)

There are many many of these available in lists at various sites around the Internet.

A