Digital Hell is the rather light hearted name I've given to a whole series of technical exercises. Each one is designed to address a specific aspect of guitar technique and give the most efficient return on your time and effort. Normally you'll be working on these one at a time in anticipation of a core musical subject so that when the time comes you can execute it with some degree of ease. That way you can focus more on the musical side of things.
Here's an example. Below you can view the accompanying video too.