Some users still prefer Firefox to Chrome because of AdBlock Plus extension (though less powerful ABP is available to Chrome) which is most popular and number one extension that has crossed 3 billion downloads recently in AMO, there are other Adblocking extensions available for Chrome and Safari, the most popular one is AdBlock which is now available for Opera in Opera add-ons catalog for download.
AdBlock automatically blocks ads in Opera,no configuration is needed
Let me tell you I’ve tested this add-on and impressed!. No configuration is needed, install the extension and forget about ads. Though ABP not available for Opera but much powerful AdBlock extension here for Opera users to please them.
You can right click on its toolbar button to access its preferences. Custom filters for this extension are updated automatically.
Advanced users can create their own filters and subscribe to arbitrary lists. You can whitelist the domain that you want to see the ads by visiting AdBlock options and clicking on “Customize” tab. This extension works on secure pages also.
Some volunteers contribute to AdBlock project maintains list of known ads, this extension reads these lists and prevents ads from loading in Opera browser.
AdBlock works perfectly and fully to its ability in Opera 12.50, where in older and current version of Opera (12.0.2 ) some features may not work due to that some ads still be shown.