Codacy - Automatically reviews code style, security, duplication, complexity, and coverage on every change while tracking code quality throughout your sprints.

Don't Make Me Think - Originally written in 2000, Don't Make Me Think is one of the original books on web design and usability. Although it's been around for a while, the goals and lessons of the book are universal and apply to websites today.

SonarQube - SonarQube, a core component of the Sonar solution, is an open source, self-managed tool that systematically helps developers and organizations deliver Clean Code.

Coursera - "Compilers" by Stanford - The course explores how high-level languages are compiled to low-level assembly.

CodeClimate - Code Climate provides automated code review for your apps, letting you fix quality and security issues before they hit production. We check every commit, branch and pull request for changes in quality and potential vulnerabilities.

The Elements of Typographic Style - The primary form of communication on the web is through text which makes typography one of the most important aspects to design for.