For those of you on Mountain Lion, Mavericks, or Yosemite using Apple's built-in Apache web server, you can set Apache to automatically start when your Mac starts up. Just run the following command in a Terminal window.
sudo launchctl load -w /System/Library/LaunchDaemons/org.apache.httpd.plist
Note: that command should all be on one line.
To stop Apache from starting automatically, run this command...
sudo launchctl unload -w /System/Library/LaunchDaemons/org.apache.httpd.plist