First remember that “Internal Server Error” does not mean a server problem. It implies an “internal” problem inside of your own hosting space and files. Here is a quick overview of what will solve this problem, and then followed by step by step on how to do it:
1. .htaccess file has problems
In the (dot) htaccess file, you may have added lines that are either worded badly or conflicting. The best way to troubleshoot this is comment out the lines in the htaccess.
You can comment out a line in the .htaccess by adding # 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
AddType application/x-httpd-php5 php
Then try something like this
#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.
2. Bad permissions, Writable by group
One or more files or folders have permissions higher than 755, which is not allowed by the server. Any software that says you need 777 will work with 755 on our server.
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.
3. Your PHP version is wrong inside the “PHP Configuration” section.
4. Your username does not own the folder or files.