Firefox might be your chosen browser for its speed, useful add-ons, and open-source culture, it’s also packed with many useful built-in features.
Here is one of them in which you can open multiple web sites at launch on Firefox.
You know that you can set one home page when browser launch. Now in Firefox you can set multiple websites as home page when Firefox launch. For example you may like Facebbok and Twitter to launch every time you open your browser.
In Firefox, go to Options > General. In the home page field, enter URLs separated by pipes. For example “http://www.facebook.com | http://www.twitter.com | http://….” and so on. Then, hit “OK” and relaunch your browser to see the magic happen.