Here is the code from Twitter:
<a class="twitter-timeline" href="https://twitter.com/Stockton_edu" data-widget-id="289837535046279168">Tweets by @Stockton_edu</a>
<script>!function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs");</script>
This is what WP does to it.
<a class="twitter-timeline" href="https://twitter.com/Stockton_edu">Tweets by @Stockton_edu</a>
!function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs");
For security reasons, WordPress does not allow <script> tags inside a post or page. Take a look at this page for ways to load Javascript on individual pages:
http://codex.wordpress.org/Using_Javascript