Just using Firefox doesn't offer any security benefits, but using the NoScript addon with Firefox does offer an important safety upgrade. NoScript addon for Firefox is developed by Giorgio Maone and is available for free from the Mozilla addon site. NoScript blocks active scripts from websites unless you specifically allow that site. For example, if you visit google.com, scripts from google will be blocked. To unblock a site, simply click the NoScript options button in the bottom right corner of the browser and select "Temporarily allow sitename".
Never select 'Allow Scripts Globally' as that would be defeating the entire purpose of NoScript. On some pages, you may need to temporarily allow more than one site. Always be sure you're only allowing the legitimate third party sites that are required. For example, when viewing a video on YouTube, you'll need to temporarily allow both youtube.com and ytimg.com.
If you're unsure about a particular site listed, use your favorite search engine to research the sitename. If there's any hint that one of the sites listed may be malicious, don't grant permissions for scripts to run from that site.
Used properly, the NoScript addon for Firefox offers considerable security benefits. Firefox users can further bolster their online safety by disabling HTTP header refresh in Firefox. While you're at it, you may also want to disable Google/Firefox prefetch.