Istantiate CKEditor into ASP.NET page

Hi! I need to istantiate CKEditor into my ASP.NET page. I've tried to create a textarea tag and below that i've inserted this script tag:

<script type="text/javascript">
CKEDITOR.replace('my textarea tag name');
</script>

Into the head tag i've already inserted the javascript file "ckeditor.js". Running the ASP.NET page the CKEditor doesn't work.
Why?

Thanks for your help!