In Firefox 6 (beta) on OS X 10.6.7, I Cmd+click to open links in new tabs. This almost always works. However, I've noticed that with certain links, the new tab opens properly but the current tab will also redirect to the link's URL. For instance, the text links in the body of this post have this problem. Does anybody know why?
There are some things like Buttons where you're at the mercy of the site developer whether if it opens a new tab or new window. You can change your firefox settings to open new windows in a tab to try and couter this.