If a form control causes something to happen when a user tabs into it, this could be confusing for people with cognitive disabilities or people using assistive technologies, such as screen readers or screen magnifiers. For example, if a form field causes a new window to open when it is tabbed into by the user, the user may not realise that this has occurred. Alternatively, the new window may overlay the existing window and the user may not understand what has happened.
Ensure that any change of context that is caused by a form (e.g. a change of language or submission of a form) is only triggered by a specific action, such as pressing a submit button or clicking on a link. If a change of context must occur automatically, try to ensure that the user is clearly notified.
//This is an example of how a form control should not be used. The form is submitted when the selected option is changed. There is no submit button for the user to press
<form id="language_selection" action="submit.php" method="post">
<select name="lang" onchange="lang.submit();">
<option>English</option>
<option>French</option>
<option>German</option>
<option>Arabic</option>
</select>
</form>