HTML, CSS, PHP and jQuery. With those four languages you can build anything.
Now, there are plenty of forums already out there, so you may want to consider extending a forum that is close to what you like with additional features via plugins.
If that's not possible, then take a look at a framework (Yii, for example), which should significantly speed up the build process, as it comes with tools any website/application will most likely need.
Hi, I'm interested in building my own user friendly forums and the extent of my coding skills is just a basic understanding of HTML.
I was hoping someone here could tell me exactly what I need to learn in order to make this happen as soon as possible.
Thanks in advance!