is the revision "A" of the standard titled "Generic Requirements for Surface Mount Design and Land Pattern Standard." Published by IPC (the Association Connecting Electronics Industries), this document superseded the original IPC-7351 and laid the groundwork for modern SMD footprint design.
One of the most common mistakes engineers make is using the "nominal" dimensions from the component datasheet. If your passive 0402 resistor has a tolerance of ±0.1mm, and your footprint is cut exactly to the nominal size, half of your incoming parts will not fit correctly. ipc7351a