Adding custom CSS to Magento Homepage

Adding custom CSS to Magento Homepage

I'm trying to add a css file to my CMS homepage by going to CMS > Pages >
Home > Design then updating the Layout XML however it keeps adding in
/base to the url to show the following:
<reference name="head">
<action method="addJs">
<script>nivo-slider/jquery.nivo.slider.js</script>
</action>
<action method="addCss">
<script>../bootstrap/theme_name/css/nivo-slider.css
</script></action>
</reference>
which outputs the following in view source:
<link rel="stylesheet" type="text/css"
href="/skin/frontend/base/default/bootstrap/theme_name/css/nivo-slider.css"
media="all" />
I've tried ../ and adding in the absolute link however it just adds it
after the /base/
Is there a way I can override the theme trying to add in /base/
Thanks!
Dan