By default, when Firefox starts it loads your home page. However you can also set it to the last page you visited or a blank page.

• In the location bar, enter about:config
• In the Find text box enter browser.startup.page to locate the preference
• Double click on browser.startup.page to edit it. You can enter:
  • 0, to start with a blank page
  • 1, to start with the defined home page (the default value)
  • 2, to start with the last page visited, not necessarily the current tab or window

You’re done!