This looks like the NLS_LANG environment variable (of the command prompt and not the DB) was not set correctly prior to installing the translation.
Make sure that the character set is AL32UTF8.
Have a look at the procedure here:
i've done the same operations but nothing's changed :-(
Your browser is receiving the UTF-8 codes for è, but is displaying them in a single byte characterset.
Either you browser is not configured correctly to display UTF-8 or the HTML-encoding tag of the page is not set correctly, here is how this website is set:
<meta charset="utf-8"><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
Check your browser encoding settings and the tags at the beginning of the webpage.