We have been using Opera for some time now and love it for its simplicity and speed, though Firefox will still remain the best browser for us. We have been discussing tips and tricks for Opera, such as using StumbleUpon in Opera and opening a new tab in the background.
Browsing over time in Opera, we came across a very annoying problem, Opera exited itself on clicking the main close button without prompting the user about it, so, often we had to restore the 20 open tabs we had running before Opera closed.
Firefox and Internet Explorer prompt users before closing, when multiple tabs are open. We are not sure why Opera does not have this feature enabled by default, but found a solution where we would be prompted with a message before Opera closed itself.
To have Opera ask/prompt you before closing itself go to Tools > Preferences or use the Ctrl + F12 hotkey. Navigate to the advanced tab and select browsing from the left hand side menu. In the options provided select Confirm exit.
So the next time you click on the close button you will be prompted with a message before Opera exits.
Note: Unlike Firefox and Internet Explorer, you will be prompted with this message even if you have one tab open.