Conform or not conform?

I read about building accessible websites. It seems to me that HTML 4.0 is the preferred standard. However, I am not sure whether my pages are built in HTML 4.0. I use Dreamweaver CS3 to build all my websites. And the dotype above the <head> doesn’t say HTML 4.0 (see below). Am I conform or not?

<!DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.0 Transitional//EN” “”>
<html xmlns=“” lang=“EN”>

Does anyone have an answer? I am confused with the following too:
HTML 4.0 Strict
HTML 4.0 Transitional

The default is Transitional in Dreamweaver. When do you change it to Strict?