Using Javascript on a wordpress.com hosted blog

Hi,
I have a blog located at http://ec18.wordpress.com

Is it possible for me to use javascript in a page that I create?

I looked through the codex and found that help on JS usage confusing. The script I am trying to use is

<script type="text/JavaScript" language="JavaScript">
<!--
function expand(param)  {
document.getElementById(param).style.display=(document.getElementById(param).style.display=="none")?"":"none";
}//-->
</script>
At the top of the page and for individual instances of the above

<a href="javascript:expand('dir1')">
                                Text you want clicked >></a><br />
                               <div id="dir1" style="display:none"><br />
                               Text you want displayed when the above text is clicked.
                               </div>

The purpose of this is too have a dropdown when a link is clicked.

I have tried adding this to the page but when I save the page the top Script part disappears and in the second part all > get converted to &gt

Help please?