Internal server error is not new for the majority of webmasters. It is an error that generated by your web servers. As long as webmasters encounter this error, they can clearly know something wrong, but they cannot tell the specific information of the error condition because this error is not specific to WordPress. 500 Internal Server Error is one of the most common WordPress errors that a user can come across while using a self hosted WordPress website. 500 Internal Server Error is a generic error message, given when no other specific message is suitable. There can be number of reason for a 500 Internal Server Error to display in a web browser.
Following Reasons display to Internal Server Errors
Try deleting your .htaccess as your permalinks might not work, but you’ll at least know whether this is being caused by an error in.htaccess.
I deletion of .htaccess did not work the re-upload it and add the following:
Increase the server memory in php.ini file for example from 64m to 128m
When you have changed the prefix of your MySQL database tables manually this can also affect it so revert back to your previous tables.
When you have just moved to another server/hosting and your php version is old try adding this to your .htaccess file:
ADDTYPE X-MAPP-PHP5 .PHP
Disable your brower-cache then quit tour browser then open it again and see what happens. This one is pretty straight forward.
When you Check your file permissions as some server will behave better if you set your permissions to chmod 777 instead of chmod 755 – as strange as it sounds.