The point size (pt) in html is very browser relative and I don’t advise using it. I advise using pixels or px. I have noticed, from my experience and the versions of software that I use (Windows XP and CS3) that the px in html is very close to the same size as pt in Photoshop if the font is the same and the height and width of the font in Photoshop is 100%.
Using pixels in HTML allows you to much more precisely set the size of your fonts across multiple browsers.
Abraham