How to get external link warning when cick on tweets


I need to add the class “ext” to my tweets so they will display an message that they are going to an external link. Below is my code . It does not show the class “ext” on each tweet as I need.
thank you

<div class="ext">
<a class="twitter-timeline ext"  data-chrome="nofooter noscrollbar noborders nofooter transparent"    href=""  data-widget-id="266166506696622080" target="_blank">Tweets by @FAFSA</a>
    <script>!function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0],p=/^http:/.test(d.location)?'http':'https';if(!d.getElementById(id)){js=d.createElement(s);;js.src=p+"://";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs");</script>