It's a document describing "illegal" ways of putting bricks together, which means that they are not for the designers of LEGO but amateur (as in non-official builds) builders as they are usually not as strong and using the bricks in a way not intended by the design.

Edit: if you read through the posted documents of the "Legal vs Illegal" ways of putting bricks together, some of them have description of why it's considered illegal.

For example:

"Both ends of a Technic hole are larger than the diameter in the middle. Until it ‘snaps’ into place, the half-peg is in compression and could be permanently damaged over time. Also, by not being locked into place, the element can easily pop out during play."

Edit2: actually, now when I read it again, it does seem to be a document for official LEGO designers (from LEGO designer Jamie Berard) about how to NOT design the sets. Sorry for the confusion.