# Validating the document

Validation is the process of determining if a document conforms to the specification for documents of its type.

Coda can perform inline validation of documents against the World Wide Web Consortium's HTML and XHTML standards.

To turn validation on or off for the current editor document:

- Click the warning triangle button in the bottom of the editor view

Note: Turning on validation will also cause line numbering to be turned on, if it's not already turned on.

If the document contains any validation errors, the offending lines will be marked with yellow warning triangles in the line numbering gutter. The total number of errors will be shown in the button that turns validation on and off.

If you place the text cursor in a line containing an error, a balloon will appear with the corresponding error message. The tip of the balloon will point to the approximate location of the error.

You can use the stepper arrows in the validation button to move back or forward by one error, if there are multiple errors.

As you work, the document will be re-validated whenever you pause typing, until validation is turned off.

Note: The validator only understands HTML and XHTML documents and the button will be disabled unless you're in the HTML syntax mode.