I can't ask seller a question, I'm told the (3-digit) security code is wrong It used to not work only with Opera, but now it also doesn't work with Mozilla or Firefox. And no, don't ask me to use Internet Exploder , I'm not running Windows anywhere... It wasn't important this time, I was just going to inform the seller of a mistake but it could be important later.

Assuming you're on a Mac, and this is probably a cache problem, jave you tried a hard refresh to get a new security code?
Hard refresh for Firefox on Mac: Command+Shift+R

It's not Mac. Anyway: after it failed in Opera, I opened the item page directly in first Mozilla, then Firefox. Each presented a different number. I don't think I had ever browsed Delcampe before in that Firefox. I could try to clean up cookies but I doubt this would be of help.

Sometimes I also have the same problems with "Security code is wrong" but after some tries at the end accept my code.Sometimes I need to retry 10 times the code to accept it even to see clearly the digits and to type them correctly.
Sometimes do not have any problems.I do not have any explaination.I am sure Delcampe too

Try clearing your cache, that should do the trick.

I don't think so, but just so that I can say I tried, I tried, and as expected it didn't help. I also note that the text filed where you ented the code is 5 characters wide. So, I saved the HTML, changed the width to 3, and tried to "ask" through my local copy. Tried a bit back and forth with loading my local copy, then loading the original, then entering in my copy the number shown in the original but this didn't work.

There must be some other reason it doesn't but I'm not an expert...