Good news for Opera users, what Opera lacks so far when compared to other browsers like IE, Firefox, Google Chrome is the ability to add new features to the browser through extensions, opera 11 will be released with extension support confirmed by Opera on its blog.
Opera extensions user interface :
According Opera some Opera extensions have UI elements, but not all. An extension, for example, can add a button next to the Google search field with a pop-up menu when you click on it. Other extensions have no interface but run in the background.
Installing Opera Extensions:
Opera extensions can be installed with one click on an extension and a small installation window will appear. Click install and you’re done. The user can also drag and drop an extension onto the Opera desktop if you have an extension stored on your computer.