Hi,
As shaunak says, making the code yourself for a forum is no simple work at all like making a simple website. Such a forum like the common ones you see around has too much complex code esp. for a beginner.
If you want to have a forum, the easiest way is to go to Fantastico on your cpanel where there are a number of ready made forum scripts, like SMF, PHPBB, etc & use the script there to install them, withopught writing any code! U just need feed in some little information.
After that, you log in & customize it. In Fantastico, you will also see links to the respective Forum script makers sites. There you can find tutorials & documentation on customizing them & themes, etc.
If you however want to write code yourself and want tutorials, then try googling & good luck! ... if u really write code for a functioning forum, please share it with us!
