Some Helpful Links

HTML Reference
HTML extended Symbols Includes copyrights, trademarks, etc
HTML Symbols and Entities Useful HTML codes for creating symbols like the less than sign - <
HTML5 Semantic tags Further Information on what Semantic tags are and how to use these elements
HTML5 Semantic Tags: What is Semantic HTML and How To Write It Further Information on Semantic Tags and examples

Graphics Sites
Free images Find and download free stock photos - all free for personal and commercial use
pixabay Free Image for use

Utilities
ASCII Chart ASCII Codes for special characters
Hex/RGB converter Simple utility to convert between hex codes and rgb values

3D Javascript
Missing Manual for Three.js Code examples and tutorials
Sample Artist Sample 3d Javascript Artist
Three JS org 3d in web pages using the three.js Library
Three.js Fundamentals Three JS tutorials

DOM Tutorials
HTML DOM Document Object Model 
Introduction to DOM 

Ruby
Class Site 
Getting Started with Rails