title: Jquery animate function doesn't work: Invalid keyframe value for property left
body: <p><a href="https://i.stack.imgur.com/163RG.png" rel="nofollow noreferrer">jquery file</a></p>
  
  <p>above is my jquery code. I want every time I click the frog image, it will move to the left 50 pixels. but when I run the code, it keeps saying "Invalid keyframe value for property left: +=50px"
  <a href="https://i.stack.imgur.com/d8Rqs.png" rel="nofollow noreferrer">google console</a></p>