Opera

Good news for Opera users what Opera lacks till now when compared to other browsers like IE, Firefox ,Google Chrome is ability to add new features to browser through extensions, Opera 11 will be releasing with extensions support confirmed by Opera in their blog post.

Opera extensions user interface :

According to Opera some Opera extensions have user interface elements but not all .An extension for an example  can add button next to Google search field with a pop up menu when you click on it.other extensions don’t have interface at all, but run in the background.

Installing Opera extensions:

Opera extensions can be installed with a click on an extension and a small install windows will appear .Click install and you are done.User can also drag and drop an extension onto opera desktop if you have  an extension stored on your Computer.

Opera extensions will support injectable JavaScript ,callouts,certain UI terms and a basic tabs and Windows API.