In 1998, Netscape released most of its code base for it popular Netscape Communicator browser suite under an open license. Around the same time, the Mozilla Organisation was formed, and they would later go on to release the first Mozilla Bowser, which would later surpass its predecessor Netscape in terms of features, stability and standards compliance. This development continued under the AOL banner until 2003, when it was passed over to the newly formed not-for profit Mozilla Foundation.
Firebug was initially written in 2006 by Joe Hewitt, one of the original Firefox creators at the age of 26. It seemed to stem off from the early developer tools that came bundled with Mozilla Application Suite. including the 'DOM Inspector'. Its creation gave web developers another great reason to choose Firefox as its de facto browser of choice for developing and testing websites. After all the Mozilla stable of browsers was a champion of Web Standards and getting a website working nicely in Firefox was a lot easier than Internet Explorer, the other leading browser of the time, and the one used by like it or not most people in the corporate world whose systems were licensed from Microsoft.
I was introduced and started using firebug as late as 2008. It transformed the way I and many others worked developing websites with HTML and CSS. Prior to Firebug, debugging, editing and monitoring a complex website design could be a painful and arduous process and was often a process of trial and error. This also coincided with a move towards more standard compliant driven websites used css rather than inline styling as best practice and the sepration of styling and markup.
Personally, I moved away from my reliance on defaco proprietary tools such as Dreamweaver, that enabled the deployment of cross browser markup using a series of templates and macros, to a more hands but lightweight approach using a combination of firebug, and a chosen text editor. This approach required a better understanding of html and css, but also gave front end developers more power and flexibility to control the look and feel of their sites, especially when wanting to implement a pixel perfect design into an actual working web site or page.
In 2007, Apple acknowledged the benefit of such a tool and bundled its own 'web inspector' with its Safari 3.0 release.
In late 2008, Google launched Chrome and wooed web developers by bundling its own web inspector, not disimilar to Firebug.
Interestingly enough, Microsoft had released its own Devlopment Toolbar back in 2005, just before the release of ie7 Howver as Internet Explorer was not then standards compliant, few web developers would choose to develop their website using internet explorer due to the number of known rendering issues.
Today it seems FireBug has become a victim of its own success with most browsers now shipping with thier own version of this once quintessential tool for anyone working with HTML and CSS. This also includes FIrefox itself! I personally find that these often conflict with Firebug making it unusable. Hence the need to learn each of the Browser vendors inbuilt web inspector or 'Firebug'. It is tempting to criticise Firebug for not keeping up with this wave of browser changes and improvements, but as some would say, imitation is the sincerest form of flattery. Firebug, although becoming increasingly difficult to install and use especially cross platform changed the way the web was built and continues to do so today, albeit in different guises.