operasearch
In Firefox you can highlight a word on a web page, right click, and google it. The results opens in a new tab in the background.
Opera has the same thing, the only problem is that it opens the results on the web page you are currently viewing. How can you make it open in a new tab (preferably in the background) like Firefox?
Navigate to about:config in the address bar, filter to browser.search.openintab and set it to true. This will open search results from the search box in a new tab.
You can also press Alt + Enter when searching to open it in a new tab.
Just tried the js hack, indeed it doesn't work by default on HTTPS. But you can turn on User JavaScript on HTTPS pages: http://www.opera.com/docs/userjs/using/#securepages
Best Answer
What Opera version are you using? According to this thread, searching using the context menu always opens in a new tab - which is the behavior I am seeing with 10.51, regardless of whether "Reuse current tab" is checked in Preferences -> Advanced -> Tabs (although it does affect searching from the search box).