Tara on "Help HTTP500 shut my site and login down?"

You get 500 error message when a user tries to access your Apache or Lighttpd based dynamic php application. It is very generic and can be caused by various problems including server errors. Here are some thing you can try to solve it:
- Your first step should be checking your site's error logs for a more specific error message. If you need help locating them, ask your hosting provider to help you with that.
- check with your host if the domain name is configured properly to point to public_html folder.
- It may indicate .htaccess issue. In most cases it is an invalid .htaccess directive. Regenerate .htaccess, and be sure the encoding in your text editor is Unicode No BOM.
- It may indicate a problem with the configuration on the server. Usually your hosting company tech support can help.
- It may indicate limitation imposed by file system and server software.
- It may indicate missing php.ini (or cannot read php.ini file).
- A malformed php cgi script.
- it could be problem with the plugins, try resetting the plugins folder by FTP or phpMyAdmin.
- it could be a problem with the theme. Momentarily, try switching to the default WordPress theme via FTP or whatever file management application your host provides by renaming your current theme to rule out any theme specific issue.
- If the above troubleshooting steps fail to resolve the issue, try manually re-uploading all files and folders EXCEPT the wp-config.php file and the /wp-content/ directory from a fresh download of WordPress. Make sure that you delete the old copies of files & folder before uploading the new ones. Read the Manual Update directions first!