Under Options -> General -> Startup, I have the action set to "Show my homepage".
However, every time I open up Firefox 4 it opens up my last session's tabs. I tried restarting, changing from "Show my homepage" to "Show my windows and tabs from last time" back to "Show my homepage" to see if maybe the option was just a little screwy, but I can't get it to stop opening up my previous tabs.
Is there another option I'm missing? I didn't have this problem with Firefox 3.6.