Hi,
You should find all the information you need about CAS in the forums and in the wiki (http://wiki.liferay.com/index.php/Main_Page). And of course on their official web site (http://www.ja-sig.org/products/cas/)
To your second question: create a page in Liferay, and set a friendly URL (You can do that in "Manage pages").
In this page, add your portlet.
Your URL should be similar to this one: https://www.liferay.com/web/guest/community/forums
Without the friendly name, it would be: https://www.liferay.com/web/guest/community/11
Where '11' is the page ID...
As you can see, the message board portlet is displayed. Just imagine you configure your page with a blank theme and no border, and the integration into an Iframe should be ok.
Simply write this code in any HTML file, and you will see the result.
1<html>
2<head><title>Demo Iframe - portlet</title></head>
3<body>
4<h1>Below is the iframe</h1>
5<iframe scrolling="auto" frameborder="0" width="100%" height="800" src="https://www.liferay.com/web/guest/community/forums">
6<h2>Your broser does not support IFRAMEs</h2>
7</iframe>
8</body>
9</html>
Regards
Hervé
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