yeah i got a question regarding abs too.... i notice that with every other muscle, after working them out they're visible and pumped... everytime i'm done with abs they disappear. is this good/normal?
As far as them disappearing after a workout, I wouldn't worry about that what so ever. Some people's muscles can stay "pumped" longer than others. Just work them hard and you can assure yourself that your are targeting them properly.
Keep in mind that your ab definition and visibility is only as good as how lean you are. You can work your abs all day long and not "see" the results if they are hidden behind belly fat.