<button type="submit" id="submit_button" disabled>Sign Up</button> /JavaScript function that enables or disables a submit button depending //on whether a checkbox has been ticked or not. function terms_changed(termsCheckBox){ //If the checkbox has been checked if(termsCheckBox.checked){ //Set the disabled property to FALSE and enable the button. document.getElementById("submit_button").disabled = false; } else{ //Otherwise, disable the submit button. document.getElementById("submit_button").disabled = true; } }