This video covers testing an HTML page with the W3C Markup Validator.

Open a browser and go to http://validator.w3.org. You can also access this tool by clicking "Markup Validator" at http://www.w3.org/QA/Tools/.

This is the W3C's Markup Validator tool. Click the Validate by File Upload tab.

Use the browse button to locate a webpage file you want to validate.

A validation page will appear. You receive an appropriate message about whether your file has passed or failed. The chosen file here passed the validation test.

Now, go back to the Markup Validator page and do another Validate by File Upload.

Find another file to run validation on.

This time, we'll use a file with errors in it.

With the file selected, click the Check button.

Here you can see this file has 5 errors and 3 warnings. You can scroll down for an explanation of each of these issues listed by line number.

Note that multiple errors or warnings can be caused by a single misplaced tag.

You have used the W3C Markup Validator to validate webpages. This is one useful way of identifying problems in your code, which you can now fix in Dreamweaver.