Originally Posted by: micha999i didnt understand the counting of the intervals in the "intervals for beginners:lesson 3"
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First & foremost, that is an introduction to the idea of intervals. If all of that is all new to you, then just take this info away from the tutorial as the main points:

1. We measure distances in music as intervals. From one note to another note is some distance that we call an interval.

2. The basic intervals (or units) that we use to measure the distance between any two notes is a half step (a distance of one fret) and a whole step (a distance of two frets).
[QUOTE=micha999]how's the "B" in the second fret, and the "C" in the third

This is a result of the fact that you can play the same note in more than one place on the guitar.

Look at the fretboard diagrams on the lesson page below the video. In the 1st pattern (furthest left), the notes A, B & C are on the lowest E string at the 5th, 7th & 8th frets.

E |---|---|---|---|---|---|---|---|---|
B |---|---|---|---|---|---|---|---|---|
G |---|---|---|---|---|---|---|---|---|
D |---|---|---|---|---|---|---|---|---|
A |---|---|---|---|---|---|---|---|---|
E |---|---|---|---|-A-|---|-B-|-C-|---|

However, if you count back 5 frets & up one string, you will find you can play the exact same notes on the A string at the 0, 2nd & 3rd frets.

E |---|---|---|---|---|---|---|---|---|
B |---|---|---|---|---|---|---|---|---|
G |---|---|---|---|---|---|---|---|---|
D |---|---|---|---|---|---|---|---|---|
A |---|-B-|-C-|---|---|---|---|---|---|
E |---|---|---|---|---|---|---|---|---|

Does that make sense?

Hope that helps! If not, please ask more. :)