Lion Web Sharing not working

[MysteriousEnoch]

So, let's say I thought of making my MBP early 2011 running Lion (Not LION SERVER) to be a HTTP host. I'd like to switch Web Sharing on in System Preference but it won't turn on. I pressed on the check box, and after 1 second, it became unchecked again. It showed on the right hand side that it is "starting" but then it changed back to "Off". How strange it is. I've tried for hundreds of times (really!). I don't wanna change ~/System/Library/LaunchDaemons/org.apache.httpd.plist cuz it actually caused the problem of MBP not booting up. Any other methods will be fine. Thanks!