Find W3C Markup Validation Errors

When you test a page for validity online at W3C validator, you will see success or a list of errors.

If you receive a list of errors, you can find out where it is.

To find where the code is,
1) Click the source checkbox
2) Revalidate the test.
3) Go to the line to see the errant code.
4) Go to the html or php file and edit or move the errant code.