Gergő,
Looks like this specific character is not in cp1252 codepage. You can use the ISO-8859-2 to store that character in the file.
You can use the encodings that are not in the list by entering their names manually into the combobox.
What editor are you using? Note – for some files (XML, JSP, HTML) it may not be enough if you manually set encoding in the file property. The encoding should be specified in the file itself or the file can become unusable.