[otrs] Issue : when opening ticket, browser prompts to open/save the html of article

Hello, I am new to OTRS, my context is that I'm transferring an OTRS 3.0 to a new machine (there is custom dev for pgp that I don't master inside). I not only copied the /opt/otrs but also the content of the DB. I checked for the dead links to see that some necessary JS was hidden in /etc/javascript-common. This is corrected and the system is working. Even email fetching is working :) and email tickets get created But I have an issue, rather weird. When open I open a ticket, the browser prompts me to open/save the html of article (which is correct) instead of showing it in the same page. Thank for your help Jerome