Can I end all httpd processes? (OSX, 10.7.4, Lion)
Mountain Lion removed the Web Sharing option, maybe you upgraded and had it running some time in the past? Anyway, you'll need to open Terminal for this:
sudo killall httpd
sudo launchctl unload /System/Library/LaunchDaemons/org.apache.httpd.plist
The first will fail if you've already killed all the processes, the second disables startup.
Open the Sharing preference pane in System Preferences and uncheck Web Sharing.