If the error 500 Internal Server Error appears on the page of your website, it is possible that you have wrong rules passed in the .httacces file on your website, if the error appeared after the upgrade from PHP4 to PHP5, please review the settings in httptacces to be compatible with PHP5, delete the previously set rules and put them back one by one to test where the problem was coming from.
If the error appeared later, it is possible that you have a programming error in the script, if you have errors on ftp, an error_log file will be created where the errors will be indicated.
