You can't be too old as even those of use in our 30's have seen/used each of those items. Now you are really old if you have a slide rule and your rubber company algorithm book.

j/k= joke
rofl= rolling on floor laughing
brb= be right back
lol= laugh out loud
ttyl= talk to you later

shoot....lets start that thread....how many of these can we come up with and please include definitions so we can all learn to be lazy and barely comprehensible.