Here’s a little round up of some verification & validation tools for checking HTML, CSS and Javascript code.
First up the have the original Markup Validation Service provided by W3C,the web standards people.
This one is good for checking your HTML tags, checking the markup against the W3C vaildation rules and providing you with a list off errors to fix. W3C Offers a full suite of tools for all sorts of QA stuff, click here to see them.
Next up is HTML Inspector “HTML Inspector is a code quality tool to help you and your team write better markup. It’s written in JavaScript and runs in the browser, so testing your HTML has never been easier.” I cannot describe it any better than they have. Check it out.
CSS Lint is a great tool to validate your CSS, I’m not 100% sure it’s rules on the ‘calc()’ command are correct, however the advice and information you are given afterwards is generally very good – it will help you code better!
Finally, heres a little Javascript tool to detect errors and problems in JS called JS Hint.