For designing a web-site, you need at least 2 persons.
First, the designer. He decides on the look and feel of the site. How it will look. Basically, he designs the interface. This fellow needs to learn Photoshop/Coreldraw/GIMP.
The second person is the coder. He need to sit and implement the design. He needs to write the code i.e. HTML, PHP, ASP, Javascript, etc.
Someone can know both the skills. But in my opinion both are specialised jobs. Decide which one you are more interested in and follow that path.