Master Multiple Firefox Profiles for More Productive Browsing

One of the most powerful features in Firefox is also one too few people know about: the ability to create and use more than one profile at the same time. Here’s how to streamline and reap the benefits of multiple browsing profiles.
Instead of installing every single extension for every task into the same Firefox profile, why not separate them into separate profiles, organized by task? Think of Firefox like an Operating System for the web, and each profile as a separate application—one profile is used for basic web browsing, another for writing, another for web development, and so on.
Most of the writers at Lifehacker HQ use different profiles for writing, researching, and personal browsing on a daily basis. It keeps your Firefox instances running smoother, and each profile is streamlined for accomplishing the kind of things you want to accomplish with that profile….”

: Lifehacker