These images should print with exactly the same dimensions,
else the printer isn't making the same dpi on each axis !
 
 

qrs2620d.gif

634x576 pixels; HTML size defined as W: 201, H: 180
 
 
 

QRS2620dr.gif

576x634 pixels; HTML size defined as W: 180, H: 201

634/570 is approx 1.1111 =  201/180

I have no idea how the web browser knows what size to print the image  !!
If the whole process tells the printer that it should be 300 dpi, then the image should measure 2.113 x 1.900 inches.
My laser printer yields 2.115 x 1.890 inches -- pretty dern close.
Carole's little color printer also comes close.