How come when i click "image","maps", "news" etc. on Google i get a new window for each catergory?

I only want the click a catergory open from the orginal window, not from a new window.
How come when i click "image","maps", "news" etc. on Google i get a new window for each catergory?
If you are using a browser with add-ons, such as Firefox with Tab Mix Plus you may have changed the settings so that this happens. You can reverse these changes, or if you can't work out the root of the problem you can use something like Firefox with Tab Mix Plus; change the settings to open all links in the same window.