This Page Has Links to Programming Related Websites
The W3C HTML Markup Validation Service
Explanation of the error messages for the W3C Markup Validator
The W3C CSS Validation Service
W3C Cheat Sheet is for looking up HTML and CSS codes. Also has Mobile website design tips.
HTML 5 Reference
HTML5 Symbol Codes
HTML ASCII Reference
Visual C# (and all the other Visual software - C++, Basic, etc.)
Developer Tools (editors/compilers)
Notepad or any other text editor which is available in your StartMenu somewhere.