With our product WEB, several clients share the same server. There is a timeout of a maximum of 90 seconds for CGI scripts (PHP, Perl, etc.), so that one client cannot take over the entire web server capacity and consequently interfere with the hosting of other customers on the web server.
When you are starting an HTTP upload, the browser is sending the file continually to the web server. Your upload script is running there and receives the posted data. If you want to transfer a very large file or have a bad internet connection (e.g. over a slow modem), it can happen that transferring the file to the web server takes more than 90 seconds. But since all scripts are automatically terminated after 90 seconds, the upload script will also be terminated, before it can receive all of the data and recreate them as a file at the target. Therefore, there will be no more output from this script, the browser window remains empty or white without comment.
This can be fixed by either a faster internet connection or the transfer of large files with FTP (which does not have a 90 second limit) to a specific upload directory which, in turn, can be accessed by a script to move the image/the file to the correct folder and, if necessary, to enter it into a database.