This week marks an important milestone for Mozilla, who is celebrating five years since the initial release of Firefox. Version 1.0 made its debut on November 9th, 2004, seeking to replace the Mozilla browser with a lighter, quicker alternative. It soon became clear that Firefox wouldn't be up against just Mozilla's own software, but also a direct competitor of Internet Explorer – and for the first time since Microsoft ousted Netscape Navigator, a third party browser proved to be a serious contender on the desktop space. That fight is still ongoing, Firefox holding on to varying degrees of market share ranging from a quarter to a half of the entire market based on where you are looking.
Originally a branch of the Mozilla SeaMonkey suite, Firefox's initial intentions were to avoid the bloat and feature creep of browsers at the time. Keeping in tune with the original Mozilla browser, Firefox was built with cross-platform functionality and extensibility in mind. The latter played a huge part in Firefox's success with the sheer number of browser extensions available for Firefox being staggering.
Five years after launch, Firefox has made a name for itself and earned a reputable position as the number two browser in the world. Only time will tell if Firefox has the staying power to remain on top (or close to the top), and whether or not Microsoft can out-gun Mozilla as the evolution of browsers continue. Given that the nature of the Internet is likely to be vastly different five or ten years from now, it's hard to say for certain if any software we use today will still be around.