localhost is currently unable to handle this request. HTTP ERROR 500

The error is too generic and does not tell you exact problem. What you need is to find out what is the real issue. If your site is serving a Internal Server Error, this can be caused by a number of things, such as:

• Errors in .htaccess files
  
• Server permission
  
• Server timeout
  
• Script timeout
  
• Or some other Web Server Issues
  

Normally, a permissions issue on the file (or files) would be one cause of the 500 Internal Server Error. The simple solution is to run chmod 644 on the problem file(s) or chmod 755 on the directories.

Code:

$ sudo chmod -R 777 /"your files location"

The best way to debug the error depends upon the server and what's actually running at the time. Consider some debugging tips to help diagnose and fix common causes of this problem.