Thank you for your answer.
1) Without setting display:none for the gallery tab, video tab is still invisible, even if z-index is higher, and Visibility for gallery is set to invisible.
2) This is not possible, because all page is responsive.
3) Page is loaded with gallery tab open by default, so it is not possible to load gallery on click. But may be it is possible to force gallery to refresh dimensions each time when the 'photo' tab is clicked?
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