Firefox has gained a cult-like following for its speed, stability, and interface, but to diehard fans, third-party plug-ins remain by far its biggest selling point. Like adjusting the mirrors in a car and fixing the seat height before you leave the driveway, customizing your browser can make you feel a lot more comfortable on the Web. And like setting cruise control, a lot of them can make certain tasks a lot easier, too. Unfortunately, the endless pool of add-ons out there can also be quite daunting for first-time users who aren't sure what they're looking for. We've cut through the clutter to round up 10 of the most useful add-ons out there.