I've been using Firefox as my primary browser for so long that Internet Explorer looks strange to me on those odd occasions when Windows Update or some other automatic Windows setting opens it. There are lots of reasons Firefox is my browser of choice, not the least of which are the great free add-ons for the program that neither IE nor any other browser can match.
Topping my list of Firefox extensions is NoScript from InformAction and Giorgio Maone. The fact is, I'm so accustomed to NoScript that Firefox wouldn't be Firefox without the little blue "S" in the bottom-right corner (sometimes with a red slashed circle, indicating that a script on the current page has been blocked). The extension lets you control which scripts run on the page, so you can allow those from the hosting site, but block those from ad networks, for example. NoScript is free to download and install, but it's donationware, so if you try it and like it, consider contributing a few ducats to the author to show your appreciation.