Free W3C Markup Validation Service
The World Wide Web Consortium (W3C) has been a great gatekeeper of HTML standards. The also offer numerous useful tools to help you keep your HTML within those standards.
You can use the free W3C Markup Validation Service to catch obvious problems with your code. Keep in mind that their standards are very high, so try not to sweat the small stuff.
How to Use the Free W3C Markup Validation Service
- Go to http://validator.w3.org
- Enter your website address in the Address field.
- Click Check
The validator checks your code and returns a report with errors and/or warnings. It is going to look like it’s a miracle that your website is even up and running but don’t worry too much. Read the report carefully and evaluate whether the errors and warnings are really important.
If you see major errors, fix them and then run the validator again. If you’re not sure what the errors mean, go to the W3C Error Explanation page.