Online Tools

HTML COLOURS – Online Colour tools

The HTML online colour picker allows the user to create any colour imaginable and returns a hexadecimal value for the colour.
W3C Online HTML Colour Picker – URL outdated – previously – http://www.w3schools.com/tags/ref_colorpicker.asp

The HTML Colour Names page offers a list of colours and their respective names. The use of the given colour names is compatible with all browsers.
W3C Online HTML Colour Names – supported by all browsers – URL outdated – previously – http://www.w3schools.com/html/html_colornames.asp

HTML Characters – Online Character and Symbol HTML codes
W3C Online Characters reference page – URL outdated – previously – http://www.w3schools.com/charsets/html_symbols.asp

W3C Online Reference for common HTML Symbols e.g. & @ © ¼

W3C Online Maths symbols e.g. ⋝ ⋲ ⊾

W3C Online Reference for Symbols – Greek Symbols

W3C Online Currency Symbols e.g. ₩ ₨ $ ₤

W3C Online Arrow Symbols e.g. ↛ ↥ ↱ ⇔⇼ – URL outdated – previously – http://www.w3schools.com/charsets/ref_utf_arrows.as

W3C Online Reference for Symbols – Geometric e.g. ▣ ▧ ▷◍

W3C Online Reference Symbols – Dingbats e.g. ✻❆ ✄ ✋✎

W3C Online Reference Symbols – Misc e.g. ☕ ☎ ☊ ☂ ☁ ☀ ☠ ☯ ♒ ♕ – Chess, weather, astrology, i-ching, cards, notation, hazards, yin yen, male female ect.

W3C Online Reference Symbols – Punctuation e.g. ‼ ‵ ‹

W3C Validator Overview
The W3C Validator Overview page offers a list of validators and other online tools that can be used to determine the health of your code and site.
Overview of W3C Validators and other useful tools

HTML and XHTML Validator
The HTML and XHTML validator validates all HTML and XHTML prior to HTML 5!
HTML, XHTML validator

CSS Validator
The CSS Validator, will validate all CSS prior to version 3!
CSS Validator

Mobile Website Validator
The mobile website OK tool, will validate your html and xhtml, plus page and image sizes. The W3 version no longer works, however  you might like to try the google version.
Google mobile-friendly test

Website Link Checker
The link checker will check any url(page) for broken links, remember to scroll to the bottom of the page for results.
Link Checker – Checks for broken links, URL’s that go nowhere, missing pages ect.