Mozilla is not planning any further security and stability updates for Firefox 2, and recommends that you upgrade to Firefox 3 as soon as possible. It's free, and your settings and bookmarks will be preserved.

Also, the Phishing Protection service will no longer be available for Firefox 2 users. Firefox 3 offers a free Phishing and Malware Protection service, which will continue to protect you from online scams and attacks.
The DOM Inspector is an optional tool in Firefox 2, that can be used to inspect and edit the live DOM (document object model) of any web document. This is a highly advanced web developer feature. For more information, see the DOM Inspector document on mozilla.org.

(Windows) DOM Inspector is not included in the Standard Firefox installation option on Windows. To install DOM Inspector you must select the Custom installation option of Firefox.