title: Weird thing --onclick event disappears when I switch the visual and text tab
body: <p>here is the piece of code I want to add the wordpress page: 
  <img src="https://i.stack.imgur.com/8B6dp.png" alt="enter image description here">
  But when I click visual tab and come back to text tab. The onclick event disappeared:
  <img src="https://i.stack.imgur.com/yj3pu.png" alt="enter image description here">
  <img src="https://i.stack.imgur.com/a4VeU.png" alt="enter image description here"></p>
  
  <p><strong>Can anyone explain why it happens? why do it change the code when I switch the visual and text tab! Thanks in advance!</strong></p>