On the common menu tab I have duplicate icons of the same extenion, how can I delete the duplicate?
What is common Menu Tab? I don't have in CS6.
However, to manage your extensions and to remove any you don't need then the process is as follows:
Help >> Manage Extensions
See this picture:
There is button next to the extension that allows you to remove it.
Good luck and post back if you know what is Common Menu Tab. i like to keep a note of different terminology used in these forums.
In DW CS6, the Common tab is located inside the Insert Panel.