I'm glad to see you took my advice. These boxes are where you will do your heavy lifting -- but don't worry, I'll be there to spot you. So come on and get strong -- no pain, no gain, and all that. And don't skip any box unless you are very confident that understand the material.
The material in the boxes will be proofs, derivations, worked exercises taken from my experience helping folks by email, and the exercises in which I will guide and coach you to the correct solution. Any exercise that you don't feel confident on, you should review until you do. My email tag (hahn@netsrq.com ) will be present somewhere on each box. If you are truly stumped, go ahead and email me with your question. As long as the volume of questions does not overwhelm me, I will do my best. But please, you should also do your best to answer your own question first, and then if you can't, do your best to formulate your question clearly and completely. Please also include the box title in the subject field of your email.
I will sometimes be including optional material in these boxes. The optional material will always be labeled as such, and you should have no expectation that it will be on any calculus exam. It is there because it is interesting and because it helps paint a more complete picture of the landscape you are learning. So yes, you can skip the optional material if you want, but that is not what it's there for. It's there to help you in your quest to get strong.