If your WordPress install tosses up a HTTP Error 500 Internal server error, there’s a good chance your .htaccess file is corrupted.

The only way to fix is to FTP into your server and delete or fix. Depending on your host and level of comfort, you can FTP straight in or use the browser-based FTP client many hosting platforms provide.

In your FTP client, rename the .htaccess in the root direrctory to something like .htaccess_old, and try reloading the site. If it was a corrupt .htaccess, it should load.

Log into the WordPress dashboard, and go to Settings… Permalinks. Click Save, and WordPress will generate a new .htaccess file for you. If you’ve done a lot of .htaccess customization, then copy and paste bits back in to see what broke it before.

If renaming the .htaccess file doesn’t fix your site, I’m afraid you’ll have to keep looking. Many plugins have .htaccess files in their own directories– you could try going through and renaming all of those too until you find the problem. Good luck!