Can't go next to 5/13


I can't click "Next" to go to 5/13. Although the web page can show the right content, an error message always pops up: "undefined is not an object (evaluating 'window.__runner.testWeb')". Would this be the problem?
Please check my code:

<!DOCTYPE html>
  <title>Ollie Bike Sharing</title>
  <meta charset="utf-8"/>
  <link rel="stylesheet" type="text/css" href="main.css">
  <h1>Ollie Bike Sharing</h1>
  <h3>Share Your Pedals with the World.</h3>
  <p>Need a set of wheels while you're in town? Use Ollie to pair your perfect vacation with a stylish, affordable bike rental.</p>


. i think this might be the problem , you closed it . it should be without the /


Thank you for your response, but my

element is copied from the instruction. The "Next" button is simply greyed out...