how to load custom page css

I’m trying to put a custom appointment calendar on a page. The intent is to be able to have customers request consultations both on the blog and on our e-commerce website.

In the theme header I’ve added the following script for the css:
<link href=”/calendar/calendar.css” rel=”stylesheet” type=”text/css” />

The script on the page to display the calendar is:
<script language=”javascript” src=”/calendar/load.php?view=1&cid=1″></script>

The issue:
The calendar works but there is no css styling. It appears that if the css is loaded it is being overwritten by page styling. Any ideas where to put the css statement so the calendar is styled correctly?

Thanks in advance for an advice,
Doug