This page is just a public amalgamation of all the tools I've come across for my own reference made public.
Whiteheartrainbowsoul's Web Revival Glossary: Covers common vocabulary used in web revival spaces.
Melonking's Website Guide: Melonking covers making your first page, and also things to keep in mind while website building.
Mdn Web Docs: Extensive web documentation that covers both HTML/CSS basics and how to get started with a website.
W3 Schools: Extensive documentation on the basics of HTML/CSS.
Sadgrl.online/learn: Directory of tips and tutorials by sadgrl.
BadHTML: A visual example of a website that does not follow web standards. Includes obsolete HTML and Bad HTML/CSS.
Linkrot: What is it and How to Avoid It
HTML Cheatsheet: HTML Cheatsheet.
Can I Use: Check what features are supported by specific browsers.
Markup Validator: Checks codes for errors and warnings.
Github: Cloud-based service for software development and version control using Git, allowing developers to store and manage their code.
Broken Link Checker: Checks websites for broken links.
XML Sitemaps: Generate XML Sitemaps.
Colorffy: Generate your custom color variables with our easy-to-use CSS and SCSS Variables Generator to easily create and manage your CSS and SCSS custom variables.
Sadgrl.online/learn/: Directory of tips and tutorials by sadgrl.
Matthewjamestaylor: Offers the bare bones code for literally any layout you could possibly want