@scragarAug 10.2008 — #depends on the application.
For anything web based you will need the basics, HTML and CSS.
After that it's all dependant on what you want, for added interactivity go for javascript.
For server side features like databases etc choose something like Java(for JSP), PHP or ASP( which is .NET and expensive, so if your learning not the best choice, although the jobs it offers pay the most more often than not )
@scragarAug 10.2008 — #Almost anything you give the code to can be reused, on the other hand if you want to keep something secret:
compiled applications like flash and java are very hard to reverse to get the original code back, however I wouldn't recommend using these too much, not only do they add considerable to CPU load compared to open technologies, but not everyone can actually use them for a variety of reasons(they are also very incompatible with screen readers etc).
Server side technologies are done completely on the server, before the client even gets sent the page, so your code is safe.
Regardless of what any sites tell you protecting your Javascript, CSS and/or HTML is impossible, since the code has to be accessible on the users computer for the browser to run it anyway.