To become a web developer you must first be very creative and intuitive. This is important for the design aspect of web development. Secondly you must be a person who can sit typing code for hours, following on from this you must be a good problem solver.
Overall you need patience, creativity and knowledge.
The three areas of web development:
- Design: Most commonly done in photoshop. A web designer will layout a website and create an image of what the final website will look like.
- Coding: The job of a coder begins with slicing. The coder slices the designers image into different sections then marks up the individual images using a web markup language such as xhtml. Style and formatting is then applied through a secondary code called CSS (Cascading Style Sheet).
- SEO: Search Engine Optimization. SEO is integral to ensure a website gets maximum exposure in search engines by making sure every aspect of the website can be accessed perfectly by search engine crawlers. This includes validating all markup language, well laid out code, correct use of different languages and well named files/images.
More to the point of the question. To be able to market yourself as a web developer you must be able to design creative weblayout concepts in Adobe Photohop. The program is very large and is estimated that only about 10?f its users make use of its full potential. It may take years to master such software to a professional standard. You will also need to know how to code. Start by learning basic markup including XHTML and CSS. After you are fluent in both move on to PHP and MySQL and so on. You can find great coding tutorials here: http://www.w3schools.com/
Don't worry about SEO yet. Its irrelevant until you can make a quality website you are happy to publish.
The best way to improve is to keep at it. Post your work on forums and ask for help, I recomend: http://www.devppl.com
And don't forget to enjoy it ;)