Ok, I will think of clearing the cache and deactivate the plugins next time I have a problem. You told me that before and it worked, it seems to be a basic stuff to do, but this time, only the buttons are ok now; so number 6/ is solved, but all the other problems are still there, as I mentioned in my first post: The bootstrap slider, the size of the images in the Librairie page which are really small, and the text is not going below these images (is it because I am using a table instead of columns?), and all the paddings and margins which are too large, and also how to justify the text in your tab widget.
Thanks for helping! 🙂

Hi,
I wrote back earlier, but my message is not showing after I click on the Submit button, so I don’t know if you got it or not.
I was saying that I don’t have the Image sharer plugin, but I have one that shares images and I deactivated it and the problem is still there.
Also, do you think the padding and margin problem could be related to a plugin?

Here are the other pages:

https://www.nouvellepensee.com/librairie/

https://www.nouvellepensee.com/librairie/le-secret-du-succes-1908/

P.S: The buttons are images, not css.

Ok, thank you very much! 🙂