I developed a web site with a protected download area (using .htpasswd) containing many pdf documents and download exe files. The website works correctly with all Microsoft browsers as well as Chrome and Opera. It also works correctly with Firefox the first time you open or download a file in a session. On subsequent attempts to read or download a file, I get and error of the form "C:\Users\tom\AppData\Local\Temp\0tdBH5YZ.pdf.part could not be saved, because the source file could not be read." If you shutdown firefox completely and re-login to the website, it again works one time. I use a very simple php script to support the download where the relevant function is: function Download($file) { $rtn = FALSE; if (file_exists($file)) { $rtn = TRUE; $size = filesize($file); $type = filetype($file); header('Content-Description: File Transfer'); header('Content-Type: application/octet-stream'); header('Content-Type: '.$type); header('Content-Length: '.$size); header('Content_Transfer-Encoding: Binary'); header('Content-Disposition: attachment; filename='.basename($file)); header('Expires: 0'); header('Cache-Control: no-cache, must-revalidate'); header('Pragma: public'); ob_clean(); flush(); $lr = readfile($file); if ($lr == FALSE or $lr != $size) { echo "error in readfile<br>"; $rtn = FALSE; } } return $rtn; }