Currently Being ModeratedJan 24, 2013 12:13 PM (in response to aRKay)
Download the free app TinkerTool from http://www.bresink.com/osx/TinkerTool.html
In the TinkerTool preferences, go to "Dock" and (in "Restricted Dock") check "Don't allow to modify content."
Then click on Relaunch Dock.
Thereafter, if you ever want to make any modifications to the Dock, you will need to uncheck "Don't allow to modify content."