What program is needed to build a website?

You can build site in many ways, like, you can install Wordpress blog CMS, and install some yheme from site and that's it, just add content. But if you like to build your site, than some programs are needed, like Microsoft front page, or dreamviever, than for processing pictures, and making ones, some tools for images, like gimp.....etc, this is a huge field, if you don't have specific thing in mind it is hard to answer more precise than that.