Firefox allows you to browse many web pages at a time using a very nice feature called “tabbed browsing”. Instead of opening a new browser window every time you want to view another page, you can open a new tab.
Clicking on this button (at the right end of
the tab list) allows you to close the current tab. Right-clicking
on it gives you some options such as opening new tabs, reloading
current and all tabs, as well as closing them. You can also open a
new tab through the -> sub-menu, or simply by using the
Ctrl-T
keyboard shortcut. On the other hand,
Ctrl-W
closes the current tab.