I remember when Firefox was called Phoenix. At that time, when doing web design, everyone was testing on Internet Explorer 5, which was the de facto standard in HTML and other web technologies. If the client wanted a website that was a little fancy, then you would recommend that it was built using Flash. We all knew then that Flash websites were bad for search engines and usability, but everyone was doing it.
When Firefox or Phoenix came along, it was literally a breath of fresh air. Here was a browser which, instead of trying to create its own standards, it was trying to be compliant with the W3C standards. It did take a little while for me to get used to doing things the Phoenix way, but it was worth it in the end, as the standard eventually won over the proprietary intentions of the different software vendors.
Firefox then was eventually chosen as the name of the new browser. Before Firefox, it was changed to Mozilla Firebird, as there was a trademark conflict with Phoenix, the BIOS vendor. However Firebird was also the name being used by another open-source database project, so the name had to be changed again.
Without Firefox, the web will be a lot less standardised today as some large corporation would have been able to influence the web into a space dominated by its proprietary technology. Thank you Firefox and happy birthday!