Firefox skins are known as “Personas” and basically make it easy to give your browser a distinctive look without bogging it down (they're basically just a background for the browser window and status bar). Personas are a doddle to install – take a trip to the Personas website and just roll your mouse over the examples shown on the front page – your browser will instantly change appearance to match. Click Wear It to select a Persona, or move on to another one.
You might be happy with a single Persona, but if you like to chop and change then you’ll need the Personas Plus Add-on. Once installed, the Personas Plus icon will appear in the Status bar – click this to have quick and easy access to large numbers of Personas via various dropdown menus. These include new and featured, most popular and “All”, a slight misnomer in that while you appear to be able to browse by category, only a small selection are available: if you want to view more, you have to click the option and visit the main Personas website.
You can also access recently used Personas, or sign up for a free account that lets you create a list of favourite Personas for quick and easy access. Personas Plus also features a Rotator option: select the “Random selection” option from any of the menus (including Favorites) and these will be rotated randomly every 60 minutes or so. Note that some have complained about adult skins being mixed with children’s, so use this option with care if you share your PC with youngsters.