If you want to automate going to specific web pages every time you open your Firefox browser, the add-on Session Manager might be what you're looking for. Everytime I open Firefox, I open a window for each of my web sites and for my Google Adsense, Gmail and Bloglines acccount.

After you've installed the Session Manager add-on, just open one blank window of you Firefox browser, and then start going to your favorite sites, and logging in, if necessary. Then choose Session Manager from the Tools menu and click Save Session. Name this particular session according to your own liking like 'Initial Session,' for example. Now every time Firefox opens you can choose this session called 'Initial Session,' and voila, you're automatically taken to your favorite web pages! :)