It's unbelievable how weak guitar players are on knowing the notes on their own instrument!
No other instrument suffers from this same fate. Imagine a piano player not knowing the note names of the keys...or a trumpet player not knowing what notes come out if they push specific valve combinations. Yet, an amazingly high percentage of guitar players don't know the notes on the neck.
This problem has certainly been created by the guitar world's penchant for tablature and chord picture diagrams. Despite this, there is no excuse for the failure on the part of guitar players to learn what is absolutely rudimentary on any other instrument.
If you need help overcoming this particular problem, check out my handbook Unlocking the Guitar - Notes on the Neck. It gives different approaches to learning the notes as well as drills to master the topic.