How to improve coding skills and code security?
Use Ruby on Rails as the development framework. It follows strict conventions to make sure that the quality of code produced is of high quality. Its easier to follow the best practice than not to do it. For example its easier to write unit tests than not to. Most reusable code in rails is available as plugins and and security is taken care of by the community. Its always better to use maintained code from the community, than not to. Rails and subversion make this easier by allowing code in a project to be tied to code developed by the community automatically.