ok the actual definition of "OMFB" is "oh my franking bob". it got started (as far as i know) on theblackparade.net, as an alternative to "OMFG" that some MCR fans enjoy saying. also "OMFG" can also mean (for frerard supporters/MCR fans in general) "oh my franking gerard" and "OMG is of course "oh my gee/gerard". so...yeah. thats wat it means deal with it.
OMFB is that guy over there looking at me???? OMG!!!!!