Can you explain what you're trying to do? That might help you get some better answers.
Have you tried an iFrame on the other website? Is the other website also a portal container? If yes, you could consider using WSRP.
We have a portal at "aDomain.com"
We want to integrate a page in to another site (say: xDomain.com which is not portal container, pure PHP/HTML website)
We want to integrate the one of the page in their site.
Have you tried using an iframe on one of the pages on your xDomain.com site? For example:
<iframe src="http://aDomain.com:8080/portal/public/myportal/mypage" width="100%" height="600">If you can read this your browser does not support iframes</iframe>
Yes, I've tried it now, I'm able to see the page.
Is there a way to auto login, using a Ajax Call (User credentials are same in both the sites)?
Better start a new Discussion on the forum for that one - I'm not sure.
Are you using a Single Sign On framework? That might be a possible solution.