Option Startup Mozilla

From Mozilla Firefox Help

When you open Firefox, by default your home page is displayed. Your home page
might be a commonly-visited web site, a search engine, or perhaps your email
account, but the choice is up to you. You can change your home page or
choose to display a different page or set of pages on startup in this
section.

When Firefox starts

By default, when Firefox starts it opens your home page (listed in
the textbox immediately below), which corresponds to the Show my home
page option. Alternately, you can choose to display a blank page on
startup (perhaps to eliminate the time required to load that page from the
Internet) by selecting the Show a blank page option.




As a final alternative, you can have Firefox reopen the windows and
tabs you had open the last time you ran Firefox, effectively
restoring you to where you were when you last stopped browsing the Internet.
This can be a handy way of saving what you were doing when you close
Firefox, perhaps to install an operating system update. You can
choose this option by selecting Show my windows and tabs from last
time.




Home Page

If you've set Firefox to show your home page when you start
Firefox, you specify your home page by typing it here. You can
also click any of the buttons below the textbox to choose a special home
page:



* Use Current Page sets the currently-displayed page (or pages,
if you have multiple tabs open) as your home page

* Use Bookmark sets the selected bookmark (or if you select a
folder, the set of bookmarks in that folder) as your home page

* Restore to Default resets your home page to the default home
page