Corrected entry: Towards the beginning of the film, John enters Nakatomi Plaza and finds Holly's name on the computer so the guard can tell him where she's located in the building. After John does this, the guard tells him that she's on the 30th floor and that there's no one else left in the building. Now, why couldn't he have just told him that the party was on the 30th floor and saved him the trouble of playing with the computer?
Corrected entry: What the hell happened to the cut on Al's head? He is seen being tended for a nasty head gash by an ambulance man, but this is the first and last time he is seen wounded. No cut, no bandage, nothing from that point onwards. (01:01:30)
Correction: There is no cut, it is the blood from the terrorist that fell on Al's car. And also the guy who wipes the blood asks if it is his own and Al says no.
At no point do the cops say to Al if it's his blood, and Al says no.
Correction: This is a list of people who are currently checked into the building, so obviously the guard is having him check if Holly is actually there at all, not to see where she is.
The guard also gives off vibes of 'check out this cool new feature of ours', as he could easily just have checked for Holly himself at his computer.