I'm using Google Chrome with Windows 7. Everything a link is clicked on superuser site, the target webpage opens in the current tab instead of opening in a new tab. Is this a site related behavior? Because clicking links on Facebook opens in new tab. I don't know the terminology for this type of behavior. I googled but could not find a simple answer or setting. Holding the 'ctrl' key helps but I think there should be a correct way to make it work
The setting you are looking for would be in the web site itself. If a link in a site (this one for example) is not set to open in a separate tab it will not do that unless you hold CTRL while you click, or you could also right-click on the link to see the context menu and then specify to open in a new tab.
Press control while you click to open in a new tab.
That is is the easiest solution, the other way is to install Tampermonkey, and use this script which will open all the links in new tabs. But I don't recommend you to do that because not all the websites allow to open links in new tabs.