Setting Multiple Home pages
Firefox allows you to set multiple home pages. When starting Firefox or navigating to the home page it will open multiple tabs, depending on the number of home pages specified.
1. At the top of the Firefox windowOn the menu bar, click on the ToolsFirefoxEdit menu, and select Options...Preferences....
2. If it isn't already selected, click the Main icon. The Main options panel is displayed.
3. After the ending of the current homepage put | and than start your next homepage.
* For example:
http://www.yahoo.com/|http://www.mozilla.com/
4. Click OK to close the Options windowClick Close to close the Preferences windowClose the Preferences window.
Source
Baez if you are going to do it that way go for this.
Let me google that for you