In this 12-video course, learners discover how to handle errors in Flask—a widely used web framework written in Python language—by serving a custom error page whenever a 404 error is invoked on a website. Learn how to configure a route in your Flask app so that POST requests can be submitted. Next, use the Flask debugger to record information in your application's log; convey the invocation of an operation to end users by using message flashing, and then highlight flashed messages by defining a style for them in a cascading style sheet (CSS) file. Next, explore how to install and use WTForms in Flask application to accept user input for registration, and define a login page by using field definitions and built-in form validations available in WTForms. Then include the two pages defined by using WTForms in the Flask application, and invoke the validators defined for WTForm elements to ensure that the user input is in the correct form. Finally, ensure that all built-in validators applied on the WTForm elements work as expected.