The 3 Basic Elements in Website Design are:
- Search Engine Friendly or Search Engine Optimization
- Visually Appealing
- Usable to the Visitor
Some people try to build a website by there self and some people use professional designers.
There is also a great deal of software offered online and offline (desktop software) to build a website. Some of the software is free and some of it is premium or paid web design software.
For more information see: http://en.wikipedia.org/wiki/Web_design.