Get it here:Opera has the ability to run external programs and scripts and pass various information to them from Opera commands. One use of this is to pass the address of an advert or other content that is annoying you to such an external tool and it can then edit a UserCSS file automagically and add in the advert to a blocklist. There are currently three flavours to this: the first using the large and powerful Python, the second the tiny Lua environment and the third a C++? executable (which means it does not need any additional libraries to be used).
http://nontroppo.org/wiki/OperaAdblock
Discussions in here:
http://my.opera.com/forums/showthread.php?s=&threadid=88091
Source: Neowin