Beware of surviving Apache processes that you thought you had stopped.
I just had a miserable time making some changes to httpd.conf on an Apache (1.3)/Windows installation. After making each change, I'd stop/start Apache and test the page with a browser to see if I'd mucked httpd.conf up fatally. The trouble is that I got a lot of false readings with this test, which confused me horribly. (Make change X; page works. Make change Y; page doesn't work. Undo change Y; page doesn't work. Undo change X; page doesn't work. Scream.)
It turns out that, although I'd executed 'apache stop' properly (I think), there were quite a few apache.exe processes lurking alive in the Task Manager's Processes tab. Apparently they were the source of the trouble, because killing them manually during my stop/starts eliminated my false test results.