htaccess has broken my site

by

Enable debugging in wp-config.php and check for errors.

define( 'WP_DEBUG', true );

If you see blank white screen then it means..

  1. Either you renamed your theme folder name.
  2. Some plugin is blocking access.

Enable debigging and post errors here.

EDIT

You will have to try uploading files manually.

Download no content WordPress from here.
https://downloads.wordpress.org/release/wordpress-4.0-no-content.zip

Then delete wp-admin, wp-include and other php file except wp-config.php and wp-content folder.
And upload all files from wordpress-4.0-no-content.zip.
THis should work.

Also keep a backup before deleting any files on existing website.