What is the code you are using inside the custom tab? If it is an iframe markup then it should have a width attribute. That may solve the problem.
Nope, it’s not iframe. The code looks like this:
<div class="fb-page" data-href="https://www.facebook.com/organizacja5element" data-width="350" data-height="500" data-hide-cover="false" data-show-facepile="true" data-show-posts="true"><div class="fb-xfbml-parse-ignore"><blockquote cite="https://www.facebook.com/organizacja5element"><a href="https://www.facebook.com/organizacja5element">5 Element</a></blockquote></div></div>
OK. The problem is that the Facebook javascript is rendering the social page widget after WP-Flybox collects the width parameter. WP-Flybox defaults the width to 180px. So since Facebook has not rendered the content, WP-Flybox uses a value that is wrong after the content is rendered. I see your data-width is 350. So you need to set your div or container to 350 as well so that WP-Flybox has a width to use before Facebook renders.
Put <div style="width:350px"> before your existing code and </div> after it. That should correct the issue with them not being in line. Let me know how that works. Thanks!
Yes, this helped me 🙂 Thank you.