If you are using Firefox, you should know that typing ‘foo’ in the address bar and pressing CTRL+Enter will auto-complete it to http://www.foo.com, pressing Shift+Enter to http://www.foo.net and CTRL+Shift+Enter to http://www.foo.org. In Opera browser, by default, you will only get the CTRL+Enter for auto-complete. Below are the steps to enable the Shift+Enter and CTRL+Shift+Enter in Opera (or any other key if you want to).

Open Opera, go to Tools > Preferences. Navigates to Advanced (1) dialog and then Shortcuts (2). Under the keyboard setup area, click Opera Standard (3), then Edit (4).

In the Edit Keyboard Setup dialog, navigates to Advanced (5) > Address Dropdown Widget (6). Find the ‘Enter ctrl’ entry. Double click on the right side of the ‘Enter ctrl’, copy the text ‘Autocomplete server name, "http://www", "com"’ (7) so you can easily paste and edit it later.

Next, click New (8) 2 times. Double click on the first empty field on the left side (9), enter ‘Shift enter’. For the second empty field, enter ‘Ctrl shift enter’. On the right side (10), for ‘Shift enter’, enter ‘Autocomplete server name, "http://www", "net"’, and for ‘Ctrl shift enter’, put ‘Autocomplete server name, "http://www", "org"’. Press OK on both dialog and your Opera should give you the auto-complete function as Firefox.

[Opera]