some pages of our website contains a character whose unicode value is 00B7 (=
MIDDLE DOT,183 as decimal value or · as html entity).

we send the middle dot to the navigator, not ·

pages are ISO8859-1 encoded (and <meta http-equiv="Content-Type"
content="text/html; charset=iso-8859-1"> in header)

in the file produced by HTTRACK (sun solaris), this character is replaced by
?
this problem happens on some platforms (sun solaris) and not on others (linux,
windows)

i think that perhaps there is no character corresponding to 183 decimal value
in the character set used by httrack while writing files

Do you know why and how to fix this problem ?