If you decide that the whole tabs system in Firefox isn't for you, for whatever reason, then you'll be pleased to learn that there is an add-on available which will completely eliminate every single trace of tabs and the ability to create new new tabs. The add-on is called Tab Killer and here is a brief description that was supplied by the author, SHIMODA Hiroshi:

Some people want to keep their browsing-style based on SDI applications like Netscape Navigator 4, so, this will help them. This provides an alternative to some people, who want to use Gecko based browser and don't want to use tabbed browsing feature.

While I honestly can't recommend installing this Firefox add-on -- I love being able to take advantage of tabbed browsing! -- if you decide that you'd rather go without then please feel free to check out Tab Killer's page on Mozilla's official Firefox add-on and extensions website: https://addons.mozilla.org/en-US/firefox/addon/1938