Are you talking about from a coding point of view? Or in general? If you are talking coding, then HTML, CSS and possibly XHTML would be the big three for beginning. Once you've got those aced move on to javascript, most web-dev's need that. However, you could go javascript or move towards a server side language IE. ASP or PHP. However, right now I'd recommend PHP with mySQL as a backend because there both free. Once you've got a decent base in PHP move to ASP. Thats because the only way you'll actually be able to make a living of web-dev is to be as diverse as possible and to offer as many solutions to a problem as you can. This way you would also know the pros/cons of using each language.