These checkboxes are created in HTML with the help of a special tag. // Get the checkbox var checkBox = document.getElementById("myCheck"); // Get the output text var text = document.getElementById("text"); // If the checkbox is checked, display the output text if (checkBox.checked == true){ text.style.display = "block"; } else { text.style.display = "none"; }} The checkbox is shown as a square box that is ticked (checked) when activated. So from HTML’s point of view, each checkbox in a set of checkboxes is essentially on its own. When you are handling a group of related checkboxes onclick, using getElementById may not be the most practical way of obtaining references to them. MODS: Not sure where to post. a choice between one of two possible mutually exclusive options. Check boxes fulfill another useful data input function in JavaScript for HTML5 and CSS3 programming. Pre selected Checkbox Also Read: How to Enable or Disable Multiple Checkboxes Based on Dropdown Selection in AngularJS. So to work checkbox Checked event to work as expected we need to allow AutoPostBack=true. HTML / HTML Web Forms Tutorial For Coding Beginners / How To Use Input To Create Form Fields In HTML: Easy Tutorial / How To Define Input Type In HTML (All The Values And Attributes) / Handling Checkbox Data With In HTML: Here's How While browsing your favorite websites, checkboxes appear when you need to select one option out of the many available ones. Tip: Always add the