title: html5: Significance of attribute named required in checkbox/radio
body: <p>On form submission, how could you possibly mark a checkbox/radiobutton as required?</p>
  
  <p>Source of inspiration: <a href="https://stackoverflow.com/users/187606/pekka">Pekka</a>'s <a href="https://stackoverflow.com/questions/4901410/correct-way-to-do-html5-checkbox/4901438#4901438">answer</a> to a <a href="https://stackoverflow.com/questions/4901410/correct-way-to-do-html5-checkbox/4901438">question</a></p>