TLDR : a lot of text (mostly in the buttons) was completely invisible for me this morning. I solved the problem while writing this : it was my iPad appearance preferences. 
Hello!
Yesterday night the website was working fine for me and I managed to create a body block pattern that I plan to use to see if my measurements are correct.
Today I was having issues with exporting and printing a custom pattern I created just now (but managed to print the one created yesterday) and found the help three helping with this. (Still have to make it work, but Thanks everyone).
Unfortunately I have now another problem, making everything harder: the text in some button is invisible! (including the log in ones I just used to see if it was a problem with other browsers)
Even to enter the forum I have had to accept a bunch of conditions I could not read.
— I kept thinking about solutions while writing this post. So the next part was written a few minutes after the precedent. —
I was more amused than really annoyed. And then I think I have solved the problem on my side by unchecking the automatic appearance in my iPad preferences, but maybe someone can find help in my little story?
Cheers everyone! 
Edited to add a link to the other topic I mentioned.