Web Grapic Resolution Expert Question

My partner is a great long time C and Java programmer who knows a heck of a lot about computers.

However I can't seem to get across to him that no matter what resolution you would like to see, all browsers display
images at 72ppi. He thinks my mind is just not grasping this concept correctly.

I've made an html file that demonstrates this difficult to understand principal:

http://www.alogical.com/circle.html

I've also included an .swf file to show him that vectors are resolution independent.

I also set some of the html size code in a file to "4in" rather than 400pixels which only seems to work using iExp on a
Mac. I wasn't aware that you could even us "in" for inches in html period.

http://www.alogical.com/circle2.html

Can I get any advice from graghic sages on this?

Thanks in advance.