A question about Ubuntoo web browser 'epiphany'

First, please forgive me to write in English. It is because I can't type in Korean right now.

I have used Ubuntoo and its web browser 'epiphany'. It works well now. But I have undergone something strange. When I have visit the security site, I have had a warning message which required me to accept the certificate. I do never mark the checkbox to ask me if I always trust the site because I think this might cause some bad effect on my computer. However, the warning message do not appear any more even though I visit the same site. I don't know what is wrong with me. That is why I post this. Please let me have your answers. Thank you.