X3Photo Gallery Forums

The X3 lightbox/popup is specifically engineered for images. It works for basic web pages also, but it will not work properly for full websites from mobile devices, because of restrictions in touch/scroll. As explained in the popup examples page:

Warning! Be cautious about using the popup for full websites. Some websites refuse to load inside an iframe because of restrictions, and you will have huge issues with scroll- and interface on touch-mobile devices. We recommend using the data-popup-ignore-mobile attribute if you are loading full website links that require scroll (see details in advanced section).

If the link is a full website and you need it to work flawlessly from ALL devices, you will need to use a native browser popup window: It is not as elegant as the X3 popup, but it is meant to work. The browser popup window is documented on the same page, at the bottom:
https://demo.photo.gallery/examples/plugins/popup/