It works on Firefox, but not on Chrome…
The auto popup on https://demo.4visions.nl/easy-fancybox-sandbox/ should work in Chrome just fine…
Thinking about it, an iFrame would be better. But I don’t understand the instructions: how to add a class to a link?
Adding a class attribute to a normal text link in WordPress is not possible when editing your post in the View tab. You’ll have to switch to the HTML tab. Sorry about that, it’s just the way it is in WordPress currently. I hope that will change in a future version.
When you have a thumbnail image that links to its larger version (for example, it can link to anything really) then you can select the thumbnail in the View tab and click the Edit icon. Choose the Advanced tab in the dialog window and scroll down to the link attributes section. There you can ad a class name to the link.
Can I still decide the portion of the frame?
Not sure what you mean. An iframe showing only part of the linked page content? That’s not possible with modern day HTML.
You could link with a hash tag to an anchor tag (with name attribute) on the linked page and then limit the size of FancyBox so that the rest of the page outside the frame…