To use "index.htm" or not?

[Mountain Mart]

I have just realised Google indexes the following two URL's diferently :
www.domain.com/afolder/
www.domain.com/afolder/index.htm

....and infact, although in my case the content is absolutely the same, Google has given one a PR of 5 and the other a PR of 3.

Can anyone explain what has happened here and whether I should change all references to an index page either as "/" or "/index.htm"

[abbeyvet]

It doesn't really matter which you use as long as you stick to one or the other. Google will see them as different pages at the moment, and pr has nothing to do with content, it's to do with links.