Not sure about Macs, but if I create an HTML document with one of the following CSS
/* A4 paper size, standard "office" paper size in Europe,
* landscape orientation */
html { width: 297mm; height: 210mm; outline: 1px dashed red; }
/* "Letter" paper size, standard "office" paper size in USA,
* landscape orientation */
html { width: 11in; height: 8.5in; outline: 1px dashed red; }
and then take a real paper and put in on screen of a PC with Windows or Linux, the page on the screen will be larger than the physical one. Yes, I know, this is because of screen DPI (PPI).
But is it possible to make HTML show the same exact sizes as they will be on print?