Why the span inside the button is invisible?

Alessio_Lo_Vecchio

I'm using the Facebook button style with the name of the social. But I see an inline CSS on the span (container of the name) that set it to font-size:0; anche height:1px;

I see, also, this is due to a line in library.js:
u.setAttribute("style", "font-size:0;height:1px;overflow:hidden;display:block;"),

Why this and how to resolve? Because I would make the social name visible.
Here the page: https://www.extrait.it/accedi/

Alessio_Lo_Vecchio

Resolved with the use of a custom CSS.