Internal server errors can be caused by a few different things. When you receive an HTTP 500 error “Internal server error 500” on your site, the best way to find the reason for it is to check the error log. You can do this by using the “Error” tool from cPanel. You will get it in the Metrics section of your cPanel account.
Here you will see a list of the last error messages generated by your website. In this list, you will find detailed information about each error including the date and time of the error, some information about the client receiving the error, a description of the error, and information about which folder or file is generating the error.
Alternatively, here are the most common reasons for 500 errors:
Directories and folders should be 755. Executable scripts within the cgi-bin folder must be 755. Images, media, and text files like HTML should be 644. This could be easily fixed by just changing the permissions of the file/directory in question. You can change the permissions by using the File Manager within cPanel, or an FTP client (for example Filezilla). The correct permissions are 755.
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In the (dot) htaccess file, you may have added lines that are either worded badly or conflicting. The best way to troubleshoot this is to comment out the lines in the htaccess.
You can comment out a line in the .htaccess by adding # symbole to the beginning. You are wise to save an original copy of any file before you make changes.
For example, if the .htaccess looks like
DirectoryIndex default.html AddType application/x-httpd-php5 php
Then try something like this
DirectoryIndex default.html #AddType application/x-httpd-php5 php
Broken lines and lines that start with php_flag are the most common mistakes. If you cannot determine which line is the problem, then comment out every line.
It is possible your 500 error is caused by too many processes in the server queue. It can commonly happen If you are using a low-quality host (hosting service) or hosting package. Other than that, if you are sure your host providing very good service to you then your server administrators can be able to advise you on how to avoid this error.
Poor Programming / Script
There is an error within the programming code of the script in question. In this case, it should be revised by a professional web developer who will be able to assist you further.
If you cannot find the reason for the 500 error yourself, you may ask your web developer for assistance.