Mozilla 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 left end of the tab
list), or choosing + -> from the menu, will open a new tab. You can now input the
URL or select a bookmarked site to browse that site in the new tab.
Keyboard shortcut: Ctrl-T.
Use this button (at the right end of the tab list)
to close the currently displayed tab. Click on a tab's title to display
the contents of that specific tab. Keyboard shortcut: Ctrl-W.