Since it is an extension that should be an useful tool to be applied quick, efficient and convenience for user in Dreamweaver panel,but why I'm keep on having the problem "While executing insertObject in Add New Layout 12.htm, a JavaScript error occured"????!!!" where is the htm located and how to fix? please advice. please also do not ask me to edit the css itself becoz i dunno where to look for the css, thanks!

Hello Woo and welcome to DMXZone support forum.

I guess you are outside site definition.
Please define a site in DW.
The following video tutorial will help you to do it:
How to define a site in Dreamweaver CS5
If the error still exist please clear your DW cache file.
The following article will help you to do it:
Clearing Dreamweaver's cache

Best regards : Vulcho.