Web Page Validator
A validator is a software program that can check your web pages against the web standards.
When using a validator to check HTML, XHTML or CSS documents, the validator returns a list of errors found, according to your chosen standard.
Make sure you make it a habit to validate all your web pages before publishing.
Validate your HTML files with W3C
Validate your CSS files with W3C
You will often get some errors when you run W3C validations.
There will always be some browser specific values outside the current W3C specification:
|pointer-events||Invalid property in CSS3, but suggested for CSS4.
Often used to remove hand pointer from disabled elements.
|user-select||Invalid property in CSS3, but suggested for CSS4.
Often used to remove text selection from clickable elements.
|pseudo-class :valid||Invalid value in CSS3, but suggested for CSS4.
Often used to indicates valid input.
|@-webkit-keyframes||Often used to make animations work in webkit browsers (older versions of Chrome, Safari, and Opera).|
Validate your XHTML files with W3C
An XHTML document is validated against a Document Type Definition (DTD).
You can read more about XHTML validation in our HTML tutorial.