You can set a number of browsing options in Firefox by going to Tools | Options | Advanced. The Options screen with the Advanced options appears, as shown in Figure 6-4.
Figure 6-4. The Options screen with the Tabbed Browsing selections displayed.
The first tabbed browsing option, Open links from other applications in, lets you set Firefox to open web pages called by other applications (such as your email program) in a new window, a new tab in the most recent window (the default), or the most recent tab or window. With the first selection, Firefox opens a new instance of the browser each time you open a link in another application. The default selection opens a new tab in the Firefox window each time. The last selection opens the website in the tab or window most recently created. (While this may be handy, it's not very good if you're opening a bunch of websites one after another.)
Unchecking Hide the tab bar when only one website is open displays the tab bar at all times. (Normally, it's not displayed when only one website is open.)
If Select new tabs opened from links is checked, opening a link in a new tab also makes the new tab the active one. If it's not checkedthe defaultthe link opens in a new tab, but the tab containing the link remains active.
If Select new tabs opened from bookmarks or history is checked, it does the same thing as Select new tabs opened from links, but it's for links that are opened from bookmarks or from history. (If it's unchecked, whatever tab was active remains active.)
If Warn when closing multiple tabs is checked, you'll get a warning like the one shown in Figure 6-5 if you try to close Firefox when multiple tabs are open.
Figure 6-5. Warning before closing multiple tags.