Website security must be thought about while building every level of the web stack. However, this section includes topics that deserve particular treatment, such as cross-site scripting (XSS), SQL injection, cross-site request forgery and usage of public-private keypairs.
quick NIX secure script for securing Linux distributions.
How HTTPS Secures Connections: What Every Web Dev Should Know
The Open Web Application Security Project (OWASP) has cheat sheets for security topics.
How HTTPS Secures Connections is a guide for what HTTPS does and does not secure against.
Crypto 101 is an introductory course on cryptography for programmers.