"… I usually run the Steam gaming client and do not pay a visit to the store on the website. Some users on the other hand may visit the website regularly, for instance to purchase games in different Steam stores or to make use of browser extensions and scripts that enhance the store.
"Enhanced Steam for Firefox is such an extension. It adds a couple of new features to the Steam website that users may find useful. Please note that these features become only available if you log in to your Steam account. …"
Source: Ghacks Technology Newsletter
Improve your Steam shopping experience with Enhanced Steam for Firefox -