Hi Lisa, 
I am talking about the change he mentioned today at 9:59am.
The new lesson page:
Practical Perspectives
Guitars only play notes between 80Hz to 1.31kHz. ** The second thickest string on the guitar is the note A, whose frequency is 110 Hz. Piano goes lower and higher (down to 27.5 Hz and up to 4.18 kHz (4180 Hz) on an 88 key piano) .
** NOTE: There is an error in the video - it is stated and written that the highest pitch on guitar is 7kHz. This is an error.
The content of PMT v2:
Practical Perspectives
Guitars only play notes between 80 Hz to 1.31 kHz. The second thickest
string on the guitar is the note A, whose frequency is 110 Hz. Piano goes
lower, down to 27.5 Hz, but not as high, only up to 4.18 kHz (4180 Hz).