Launch Party - S4-E3
Continuity mistake: In 2-13 "The Secret" Pam and Jim are talking about how Jim used to have a crush on Pam when she first started here. This implies that Jim was working here when Pam was hired. However, in this episode Pam says that when Jim first started working there she said, "Enjoy this moment, because you're never going to go back to this time before you met your desk-mate, Dwight." These two scenes contradict each other.
Launch Party - S4-E3
Continuity mistake: The way the numbers on the sales board are written by Andy change in between shots. (For example, the "305" is written differently, but still "305"; not that it becomes a "380" when Andy changes the number).
Suggested correction: Michael didn't establish the contract with Hammer-mill. Rather, he locked them up as an exclusive supplier. It's unknown if they were already selling the products to Dunder Mifflin alongside Staples and Office Max.
Wrong, Josh says they cannot sell Hammer-mill products as they are exclusive to Staples so therefore they wouldn't have been able to sell there products alongside as mentioned before until Michael made them an exclusive to them solely, Dunder Mifflin. Therefore the original mistake stands true.