An Internal Server Error can have multiple sources of error:
Files that have octal permissions such as 0777 can be overwritten by anyone on the server. This is not a security hole, but a regular behavior. With octal rights 0777, the group other (i.e. every user) gets the rights to the file. For security reasons, files or folders with these permissions will display an Internal Server Error. You can correct permissions on your files or folders using appropriate protocols (FTP, SSH, SCP).
Important: Normal files (PHP scripts, HTML files) should be assigned octal rights 0644, while directories and Perl scripts should be assigned octal rights 0755. Assigning higher octal rights than 0755 is not necessary and will lead to unwanted results and errors when executing scripts.
Also, the runtime of your scripts may lead to an error. The system is configured to terminate scripts or programs with a correspondingly high runtime. Please make sure that your scripts and applications are programmed to be as resource efficient as possible. These measures ensure that the servers always work under nominal load.
Another reason for a corresponding error message could be that you have uploaded (possibly unknowingly) an .htaccess file that contains disallowed arguments (such as PHP flags). Please note that files with a dot in front are interpreted as a hidden file by most server systems (Unix, Linux, etc.). As a result, these files are not directly displayed in many FTP or file management programs. With appropriate settings in these programs (see manual) you can usually display these hidden files.
According to our experience, the most common reason for triggering the error is if the script was not uploaded in ASCII but in binary mode. Please transfer your scripts only in ASCII mode to the server and make sure that there are no Windows control characters in the script code.