Tabs Options Mozilla

From Mozilla Firefox Help

New pages should be opened in:

This optionpreference controls whether links from other applications or from
web pages which request to open them in new windows are opened in a new
window or a new tab in the most recent window.

Note: If you have chosen to open pages in new tabs,
Firefox will ignore this optionpreference and will open a new window
from a link if the page author specified that the new window should have a
specific size, because some pages can only be displayed correctly at a
specific size.



Warn me when closing multiple tabs

When you close a window with multiple tabs, Firefox will ask you
to confirm your choice. This prevents you from accidentally closing the
whole window when you intended to only close the current tab. Uncheck this
optionpreference to disable this warning and have Firefox
automatically close the window.


Warn me when opening multiple tabs might slow down
Firefox

When you open a large number of tabs at once, Firefox will ask you
to confirm your choice. This prevents you from accidentally slowing down
your system while the pages are loading. Uncheck this optionpreference to
disable this warning.



Always show the tab bar

If you're only viewing one web page in a Firefox window, the tab
bar is not normally shown. Check this optionpreference to always show the tab
bar, including when only the Firefox window contains only one
page.


When I open a link in a new tab, switch to it immediately

When you middle-click on a Web link (or hold down CtrlCmd while clicking
with the left mouse button), the page will be opened in a new tab. That page
will not be displayed and will load in a background tab. Check this
optionpreference to load and display the page in a new foreground tab
instead.