Well to become web developer, you need to know what kind of language you want to use, on which platform you need your command. The best way to learn is to go for video tutorial and follow from basic to expert.
Looks like you're just trying to pad the numbers... to someone who has no idea what they're buying that 300 number probably looks impressive. But you're taking their money to put their site in danger... disgraceful seo tactics.
If you really want to understand the theoritical aspect then you need to have sound understanding of distributed system, algorithm and datastructures, object oriented programming, database management, cryptography, software engineering practices, agile methods, MVC pattern if working with .net or have idea with php or other serverside scripting languages and networking...
If you have understanding with these modules then your career into web development is bright and can offer much into practice for making best web solution..
If you want to be a programmer or just want to create a functional websites then learn php(easier) or ASP or any server side scripting language and learn about MySql.
Basic thing you need to start:
Wanna be advanced? Get computer science or software engineering degree, I recomend computer Sci degree.